Not so attractive when they hit 40 and their face looks like a used wallet
But hopefully their tanness paid off earlier (20's, early 30's) and they're hitched with kids by that point so it doesn't matter quite as much ;-)
BTW: I don't tan at all (on purpose anyway, I have a decent tan right now just because I do stuff outside during the summer) and I'm not advocating tanning. Just playing devil's advocate ;-)