Part of the problem is the fact that internet memes often form part of the "lowest common denominator" for the community - while not everyone appreciates a multi-page article on economics or a paper on game theory, almost everyone at least quirks their lips or smiles at even a half-competently executed meme or in-joke that they recognise.
The question is, why are internet memes frequently the lowest common denominator? What is it about them that people appreciate so much, even to the inadvertent exclusion of other content?
I've been thinking about this for some time, and my conclusion is that it's our tribal instincts - just like an attraction to sweet foods and a desire for sex, we have a pronounced and built-in monkey-belong-tribe-feel-good instinct (PDF warning).
This is great and valuable, however like our attraction to sweet things, it's an evolutionarily-beneficial impulse that can run out of control when it's hyper-stimulated.
An evolutionary analogyWe like sweet foods because our ancestors were frequently on the verge of malnourishment or vitamin-deficiency, and the high-energy natural sugars and vitamins in fruit were a great boost for our survival chances. Moreover they were only intermittently available (when various fruits were in season), so it made sense for our instincts to prioritise acquiring these sources of food as we were usually deficient in them and never really had the opportunity to over-indulge to a detrimental degree.
This was fine for millions of years, but then we got smart and learned how to make doughnuts and cream cakes and chocolate bars. We learned how to spin and weave complex sugars and flavour enhancers, so we could make snacks and treats that were even more sugary and sickly-sweet than anything found in nature. We learned to hyperstimulate our natural response to sugar, but while we have a natural evolved defence against not enough sugar ("naturally liking the taste of sweet things"), because there was never a need for it we have no evolved defence against having too much.
The trouble is that our evolved instincts were only concerned with getting as much (rare) natural sugar as they could - they simply aren't evolved do deal with a world where a single dessert on its own can provide half your RDA of calories, so we tend to over-indulge our evolved instincts and binge on sugary and unhealthy foods... leading to an ever-growing increase in obesity, ill-health and the like.
Worse, by hyperstimulating our sense of taste with artificial/refined (and vitamin-free) sugars, we even lose our taste for the beneficial fruit that the instinct was originally evolved to make us eat - fruit tastes bland and boring to many kids raised on fizzy drinks, artificial chocolate and monosodium glutamate, so they reach for junk food in preference.
Similarly, we have an evolved monkey-belong-tribe-feel-good instinct. This makes perfect sense because with things like kin-selection, mate-availability, altruism, wild animal predation and disease there was undoubtedly a strong evolutionary advantage to being part of a tribe, but the upshot is that we get worried by social ostracism and get a pleasing jolt of reward chemicals in the brain whenever we feel like we belong to a tribe.
This was manifested in many ways - back in the day you used to get literal tribes and inter-village vendettas. Then as we became more civilised and larger towns developed they exceeded our Dunbar number and instead we began to identify and form tribes along other lines - for example they way people tend to incorporate their church or sports team into their identity (so they're no longer just "Bob Smith" - they're "Bob Smith, Episcopalian Baptist and New York Yankees supporter").
Later on, with mass-media and an ever more intermixed society we needed to find ever quicker, more ad-hoc ways of forming social bonds, so we also began using catchphrases and punchlines from TV and other media as a quick way to establish rapport and form ad-hoc mini-tribes with each other based around a common interest or shared context (a shared TV show or genre of music or other form of entertainment).
Finally, with the internet and social networking we have almost no default shared context - something I post on reddit as a 30-odd year-old straight white guy in Town X in the UK can be answered just as easily by a 17 year-old gay Indian woman in China as it can by someone else in my home-town.
Moreover, due to sensible privacy concerns the persistence and depth of identity is limited - no-one on sites like reddit know any more about you than you choose to post on the internet, so we resort to memes to bridge the gap, establish shared context, and establish tribes based around meme-recognition, and which website(s) and communities we visit.
This is great, but just like the sugar example, with social networks and the effectively free creation, availability and dissemination of memes we've learned to hyperstimulate those group-bonding instincts.
With memes you can always feel like part of a tribe simply by clicking a button, and as a result people do it to excess. They post irrelevant personal stories to social news sites that 99.99999% of the community have no real interest in, because when people upvote them and comment on these stories they feel like they belong. Likewise, people upvote then and comment on the stories because it makes them feel like they're part of a tribe. They've never met the person concerned, they have no relationship to them, and wouldn't even recognise their username ten minutes later, but - just briefly - they feel they have a connection, and get the jolt of social reward stimulus in their brain.
People post memes incessantly for the same reason - it's the equivalent of someone with no sense of nutrition or dietary self-control compulsively binging on junk food and sugary snacks. We've learned to hyperstimulate our instincts, but we haven't yet learned the maturity and self-control necessary to do it in moderation.
We're getting there (slowly) with sugar - we've known the basic facts of nutrition for decades, and obesity is an obvious, hard-to-ignore downside, though there are still an astonishing number of people who simply can't or won't moderate themselves and their intake.
However, as online societies or communities we're a long way from even really grasping the problem with the monkey-belong-tribe-feel-good instinct. Unlike "nutrition" there's no systematic, field of study that really even empirically demonstrates the problems with overstimulating it, and "the intelligence, thoughtfulness and educational quality of content in a community slowly descending into nothing but monkey-hooting and back-slapping" is much harder to point out and demonstrate unambiguously to people who don't already understand the problem than "morbid obesity" is.
Allied to that is the problem that at least morbidly obese people often recognise that they're unhealthy and unattractive, which at least provides some impetus to change their lifestyle. All too often people who incessantly post memes to every comment thread and derail every conversation into circle-jerking often love the content they're posting, and are hurt and surprised and dismissive of people who try to convince them to moderate their input somewhat. Like any addict, it's hard to even see (let alone acknowledge) the problem until you hit rock-bottom.
So... there we are. We've suddenly stumbled on a way to hyperstimulate our monkey-belong-tribe-feel-good instincts to the point we can feel validated and like part of a tribe simply by clicking a button, and like the proverbial lab-rat given the opportunity to self-administer drugs by pressing a lever, once made aware of the opportunity a large section of the population has trouble doing anything but hammering on it just as hard and as fast as they can.