It's because a lot of redditors came to this site when it reflected a different culture than it does now. When I first came here it was 95% programming posts, or technology-related posts. There were very few memes, and there were almost no "give me karma" posts. Rightly or wrongly people enjoyed it because it was not mainstream - it was geek stuff with very little fluff.
Nowdays a lot of it is fluff, and half of it is "give me karma" posts. Now you'll see an TV special on Johnny Depp's childhood and for the next week there will be a few "TIL that when Johnny Depp was a child..." hit the front page every day for a few weeks, then a couple a month for however long it takes for posts like that to not receive karma any more.
The problem with karma posts is the same with trolls - you feed them and they multiply. The general public didn't used to use reddit because the content was programming and geek specific. A culture grew out of it, people who used it liked that culture and it started to spread to other non-traditional geek subjects that the userbase wanted to discuss using the same culture and intellect that they discusses the relative merits of C++.
That usebase slowly changed when the Facebook generation started outnumbering the internet generation on te internet, and the content started to change from "people will find this useful" to "this will get me likes". You can see it in the titles of OC, they feed like tabloid headlines. The more they get popular the more people do the same thing to get their share of likes.
Call it elitism if you want, it's probably along those lines, but a lot of redditors want this site to be better than that - similar to how it was in the "good old days". For it to be the submitters of content need to submit for a reason other than give me attention. The site is so large nowdays that the number of people who have interesting content are vastly outnumbered by the number of people who use this site to get attention.
Likewise, the number of people who use this site to find out really interesting things is outnumbered by the people who use this site to get cheap entertainment. An analogy would be the history channel starting off with documentaries on ancient Sumer and ending up with Ancient Aliens. The people who want to see an analysis of the Epic of Gilgamesh probably aren't too impressed with the people who keep giving Ancient Aliens high ratings.