Why are so many organizations slow to approve pull requests?

Great summary.

#4 & #5 are IT with a capital I-T.

I can speak for my organization: we're understaffed and have shitty regression infrastructure. Even if some blessed soul on GitHub does a ton of good work, we still have to schedule code reviews, which is hard enough for internal staff, let alone external.

We do get to them, it just takes months. Just like our own INTERNAL pull requests. :)