Just how things are around here, really. Personally I like to use them like resumes. I can gauge a person's overall level writing with them using their biography, and can customize it to ask them what they want (ex: romance or opt out?), or even to warn them about certain facets of my Rp. For instance, I make people sign a signature with their username that confirms that they are aware that they have no plot armour and i can kill them. Painfully. Anytime I want to.

It's a useful tool. Don't have to use it, but why not?