Actually, I do use git bare repos for CD too. :) The ROOT/hooks/post-update executable can be anything, which allows to go wild : on my laptop, a push to a bare repos triggers deploy to all the machines needing it (on local or remote networks), by pushing through ssh to other bare repos hosted there, which builds and installs locally, given they all have their own post-update scripts ; all of that thanks to a git push and scripts at the proper paths. I don't think any forge could do it more conveniently.

For me the main interest of forges is to publish my code and get it discovered (before GitHub, getting people to find your repos hosted on your blog's server was a nightmare). Even for the collaboration, I could do with emails. That being said, most people aren't on top of their inbox, in which mails from family are mixed with work mails and commercial spam in one giant pile of unread items, so it's a good thing for them we have those issue trackers.