I think reddit being picture heavy is just a cause of its exploding popularity. Ever follow a subreddit from infancy to infamy? You'll see as it grows, there will be more and more posts of just pictures/memes, which in turn will cause users to complain, mods to step in to filter these out, more subreddits dedicated solely to memes about this topic, etc.

While I do think RES is awesome, most of my non-tech friends who browse Reddit (usually on their phone) haven't even heard of RES.