Have any of the people you asked been teenagers? Some of the people in the thread have suggested that its a terminology, like calling somebody dude or something, that might fade as you get older. So everybody goes through a "hella" phase, but as they and their friends age its just not used very much between them anymore.
I have no opinion on whether that's true or not actually. I was surprised the use of the term even inspired this thread. Didn't jump out to me as exceptional, so I just may not have been paying attention.