I think this is indeed traditionally frowned upon (vaguely recall reading about this) but one practical reason hasn't been mentioned: It reduces exposure to new questions asked right before a series of minor edits. Most questions receive an answer in the first few hours and then kind of disappear from attention. If they get immediately displaced by other questions and moved further down the list of recently active questions, they will get less exposure.
There are few mechanisms to counter that (you can look for them through tags and full-text search, we do periodical sweeps through unanswered question, older questions get bumped to the top, automatically or by an edit) but depriving questions of their main period of attention makes the site less useful for those who asked them. You can wish contributors would look elsewhere and find them anyway but it's just not happening so frequently, that's a simple fact.
Note that the fact heavy users can look elsewhere than the activity tab or, conversely, dislike it when they see many old questions, is neither here nor there, I am talking about the actual problems it causes for occasional users who come to ask their first question, looking at the problem from the opposite angle, as it were.