I have as many non-tech friends as engineers -- only a small percentage of the population work in this field here. There are also plenty of girls, many of whom are attractive, both within and outside the field. I mean, that latter point you can just verify by going on something like okcupid.

I would lump your response into pessimistic, based on insufficient information. Fundamentally it's one of the few I listed. The only other reason I can think of, which I may not have mentioned, is perhaps someone values very strongly living where their family is, and they are willing to suffer the opportunity cost of doing so.