Literally all of them, but look at OpenSSL for a good example.

Literally everything runs off it these days, and it's like 3 guys and a trenchcoat working on it most of the time.

It's just how open source / the industry / people are. We all have our own stuff we want to do, so as long as the stuff your using works you don't tend to care, and if it doesn't you often don't have the time or resources to do anything other than tell the owner to fix it.