If you do an edit on a question, surely you should be eligible for a share of any rep points on that question?
Similar to the usual affiliate programs.
Nope. If you are to share in the upvotes of an edited question, then you're to share in the downvotes as well. And that would discourage the editing of questions that already have downvotes. This would hurt new users the most.
Put yourself in the shoes a new user. You don't know anything about how math formatting works on this site. You ask a question that is basic for most but you genuinely don't know the answer. Your question gets swiftly closed for being "off-topic" after no one helped you with the math formatting because they were too afraid of their scores getting dinged.
Also, you must have noticed that when you crossed the 2k threshold, you no longer get the two points when your edits to others' questions are approved. At this level, we're expected to edit questions altruistically, without concern for our own scores.