Originally joined gitlab for their free private repos but with the recent downtime/sluggishness, i have jumped over to github (now that they offer free private repos too)
Gitlab is still the only viable choice for non-commercial groups who want private repos though, the 3 private members and no ability to have mixtures of public/private repos in organisations on Github is very limiting.
- a private website for my local sailing club.
- a mod for a game
- an open source project that requires a private repository for a few things
- any project relating to a private community
None of these are registered non-profits.
Bitbucket is capped at 5 users as far as I can see, and self-hosting is just a recipe for lost data. I don't know of many amateur groups that can safely host a server.