Ime, math.SE had a much friendlier vibe than most other SE sites. Primarily because you could ask about a problem you were struggling with and get help. No moderator would instantly show up and close the question as a dupe of a ten-year-old question about double integration techniques or some such.

People asking questions mostly wanted help, but most moderators thought they were curating some kind of question-answer form encyclopaedia. Very different perspectives.