Maybe it's not really missing and the APIs for LLMs are just too good and cheap to make homebrew stuff exciting.
but more likely it's going on and we're just not seeing it
in general, though, I think once a certain amount of money is involved, people just start to get rabid and everything becomes a lot less fun
It's possible to run models locally, fidget with temp etc
Being able to change other things on the fly like identify weights most used for a prompt and just changing those to see what happens is much harder.
I've tried both LLMS and image generators on my machine locally and while it's gotten in easier it's a long task just setting up. Especially if you run into driver issues.