Cranky old vampires

With vampires being the hot topic these days, I've wondered why they are all depicted as having the emotional temperment of brooding teens. It seems to me they'd all be cranky old people yelling at everyone to get off their lawn. I also wonder why they seem to have perfect recall of their lives.. I know our understanding of memory os limited but wouldn't they only vaguely remember anything more than 100 years or so in the past?