What is it with goth/punk kids and those black jackets with hoods?

I've noticed latley that there are many of these kids that wear these black hooded jackets adorned with various patches of rock bands or symbols. While that may be somewhat ok for winter ,although a little tastless, it's just bizzare for summer. Even when it's about 90 degrees outside I can still see them with those hoods over their heads. Why do they do that?