Self expression... Why do you get tattoos or other piercings...usually its a way a person expressions there self in a more predominant way instead of putting on a different colored shirt. Some people judge too soon and wrongly about people with piercings and tattoos when they shouldn't.
Well they think it looks good. It's also somewhat popular now (and was even more popular a couple years ago) especially in certain scenes, so there's that. I guess it's the reason a person would get any kind of piercing or tattoo or something like that. I don't think it's anything specific.
Stretching your ears should definitely not be about pain. If you're stretching properly it shouldn't hurt at all. If it does hurt then you are damaging your ears and could result in nasty looking or even torn lobes. I started to stretch my ears because I had regular ear piercing and there weren't to many earrings that I liked. I liked that plugs came in a lot of different styles and there were much more options for guys than a regular ear piercing. For me its not about having giant lobes. I actually hate the look of stretched ears that start to bulge out of the earlobe if you know what I'm talking about. I think 0 gauge is a good size because its not too big that it distorts the ear and there are plenty of good looking plugs at that size.