The other issue is that many novice contributors write with an improper voice and don't cite their sources - which again lowers the quality of the platform.
Stack Overflow is different, as long as a question is on-topic and not a very close repeat I think there is no great reason to close it.
I wouldn't mind at all actually. Or maybe I just miss the issue?
I guess it's one of the easiest things you can do as a mod, so if you want to do a lot of mod things... to the extent SO gives you "points" for it, it might even be engineered (on purpose?)
You can see this as a good thing, it helps you identify the most interesting questions: those that are closed!
Also, that requires fine-tuning of the "too much".
I'd expect actual spam questions to be closed automatically, similar to spam email.
- value is judged by how controversial something is, but;
- users who “crossed the line” are “not tolerated” and banned?