Ages ago an admin said "yeah it would make sense for post titles to be edited within the first x minutes of making one", an incredibly low-hanging fruit that has been requested since forever.
It still hasn't been added.
It still hasn't been added.
The first x minutes of a post are _heavily_ influential in the success of the post, editing after allows you to hijack successful titles for gain (spam)
For large subs, posts only hit the top of /new for x minutes (for small x), editing after is basically useless if it's not successful in that time
Mods patrol the /new queue as posts come in, allowing editing will complicate moderation which is already a difficult job