In addition to Shoq'sShog's excellent point, one of the main reasons reputation is linked to the ability to make edits unilaterally is that reputation is an effective stand-in for experience. You've been on the site long enough to gain 2000 reputation, that means:
- You clearly know (to some extent) how to make posts that the community deems valuable.
- You've probably read a decent number of questions and answers, and as such have some idea of what the community considers a good question.
As such, you probably know enough to make edits to correct posts to community standards. It's not a guarantee, but in the scheme of things it's probably better to have more people making edits than less; we have a lot of content that needs editing, after all.
In addition, there's relatively little risk involved here. If a 2k user starts making edits that are inappropriate, there are thousands upon thousands of other 2k users who can correct them - and odds are, will. In the rare case that a 2k user is making edits no other 2k users can see, there's always the moderator flag, plus the original poster can of course always correct any edit to their posts.