Michael Catanzaro commented:
I think the generally broken state of gnome-*-nightly is proof that nobody is really using it.
For most apps, yes, surely. It's just a direct consequence of there being no web UI to view when builds are broken, and no notifications to maintainers when builds are broken.
For Epiphany, it's my primary browser so I test it constantly and will notice quickly if there is a problem. But other maintainers likely don't do this.