Honest question, why not?

Its not like that's something that will scale infinitely, you only have so many devs and so many repos to work on, also it's not like it's hard to backup the data, actually, you can bet that you will have a updated copy of every repo on someone's machine if things really go south.

Of all things we can outsource in our infra, git seems one of the least necessary.

You don't have to though, that's what makes it so great. Just push with ssh to a directory under /var/www and you're good to go.

Having all of your issue tracking, docs wiki, build pipelines and more be reliant on a platform Ian or just comfort, it’s lock-in. If you ask a company “can’t we just switch from gitlab to github? Or the reverse, you’ll get a million reasons why it’s a huge task, because everything outside of the repo itself isn’t easily transferred.