That varies by country and sometimes even by university. In some universities there are far fewer teaching positions than staff scientist jobs, particularly when you count research institutes, while in others a typical teaching load without additional funding hovers somewhere around the poverty line.

In my case it's both, so instead of teaching I take half-time IT consulting gigs here and there, which pay enough for me to be able to do science even if I had no funding at all. I still get some grants, mostly because you're looked at funny if you don't, but I'm done losing sleep over them, plus if I finally decide to give up academia I'll have an easy transition.

But they need teaching, a day job, right?

While teaching helps consolidate your own understanding, and is useful and satisfying, it's a matter of degree.