Now I know github doesn't have a typical roadmap or backlog but I guess what I was looking for was how someone decides what feature they are "fed up" with not having.
We use GitHub to build GitHub, so typically a feature comes from our own usage pain points.
I imagine the conversation internally went something like, "Man, attaching an image to an issue is really annoying. Let's make it not suck." An issue and pull request followed, internally shipped it to test it, and today rolled it out to you all.
That's literally how 99.99% of features happen on GitHub. :)