Also, let's not forget performance. Many ads make pages take forever to load and sometimes even crash.
I don't think this is the case. Either way you might get one crash per millions of loaded ads. Making this argument just silly.
Not sure if you write software or not but crashes are more or less expected, just keep them below X% and it's "ok".
The obvious example would be sites with mediocre mobile pages fighting to serve ads. It's pretty standard to hit broken redirects, script issues, and all sorts of other crash-like behaviors visiting those.