What is up with "Senior Portraits"?

Not that I find anything wrong with them at ALL - in fact, it seems to be an additional source of revenue for pro photographers (a good thing!) that didn't exist years ago. Indeed, it's a phenomena that I only recently became aware of on this forum.

From what I can gather, there is a trend for High School Seniors to get their portraits done, usually solo shots. And not just one, posed shot, but usually a fairly extensive set of shots. The samples I've seen on this and other dpreview forums are usually of very high quality - pretty much like pro model shoots.

Growing up in the late 60s/early 70s (I'm 53), I don't think this even existed. I'm wondering - how long has this "product" been around? Is demand increasing? Do you think it's just a "fad", or something that's pretty much here to stay?
Brian
--

I don't want to achieve immortality through my work. I want to achieve immortality
through not dying. (Woody Allen)