I don't have hard comparative data, but I suspect we do have a problem the other sites don't: a lack of functional consensus on the purpose of this site.
If you've seen me on Meta much then you'll know I often complain about high-rep users who never vote, edit, flag etc, and just answer questions. Other people always respond and say that our users have the freedom to decide how to participate, which is fair, they do. But the reality is that this site has two groups of people with very different expectations of what the site scope is. The group that frequents Meta have come to the consensus position that questions without evidence of research, proof reading questions etc are off-topic. But there is another group which deem any question coherent enough to understand worth answering.
Which other sites are so divided over whether homework questions are allowed?
Now the bad questions inevitably get closed, even if they do get answers from such users first. I'd like to say that having so many users with a different position on scope sets a bad precedent, encourages those questions to be asked etc, but I have no evidence that stopping those answers would really help things much at all. But I think it does affect our moral, for me at least. Our problem isn't just that we're fighting a never ending flood of bad questions, but that there are dozens of 5000+ rep users who aren't joining the fight, and some are even actively working against us.