Well - my perspective is the KDE project, which has a team of capable admins who take care of hosting. The project has always been more or less self-hosted (I remember SUSE providing servers) and even provided hosting for at least one barely associated project, Valgrind. I think Valgrind bugs are still on KDE Bugzilla.

It's admittedly not really practical for most projects, but it could be for some large ones - Rust, for example.

I mostly work on PostgreSQL which has always selfhosted but PostgreSQL is a big project, for smaller projects it is much less practical. Even for something decently large like Meson I think the barrier would have been too big.

But, yes, projects like Rust could have selfhosted if they had wanted to.