I personally love going around reading random peoples' bios, though as the good Doctor has said, there's a sad lack of them. XD I imagine it's because people assume no one will read it, or they just don't have anything to write yet (sometimes it's hard to know a character before RPing with them a little). As someone who frequently bumps into the character limit when making character bios, though, I can't be sure about that.
As for what I put in them, I usually list gender, species, (because frequently neither is immediately evident with my chars XD) and preset link if I have one, then a paragraph or two covering history and personality. I doubt many of them are ever read, but I have fun writing them, so it's not really a loss.