Most of the updates aren't bad, indeed. But there are issues.
For example at first we had to install gitolite as well and update it. Then we switched to gitlab-shell, so we had to make the switch and now update this as well. There was resque and then there was sidekiq. There was unicorn and then it was replaced by puma and now it is replaced once again by unicorn. At some point those of us who used sqlite could not migrate to mysql when sqlite was dropped. Also more than once, when I was quick to update I ran into problems and had to spend hours in search of a solution. Nowadays I update near the end of the release cycle to avoid such issues.
I am on gentoo, so I have to create and adjust my own init scripts. I use apache, so I have to figure that out as well.
All these I guess can take anywhere from 10-24 hours per year, which can't be justified for one person. For a team it is ok.
As for gitbucket, I gave it a try and it only supports git access through http and even there it can't give read only acces to private repos. Any account that has read access, has also write access to a private repo, which makes it useless for deployment.