Why do I have a cat?

Confession: I could become a cat lady. Wait, let me clarify....I could become a cat lady and own like 20 cats if I didnt' have to have the litter boxes to go with them. Hmm...maybe I would be a cat lady on the prairie, and the cats would go outside to do their business.
I have a cat, but some days I wonder why. First of all, he is a light colored cat, and I read that light colored cats tend to bond with one person. I have found that to be generally true with Siamese, so I tend to believe that. This cat bonded with my daughter, and couldn't care less about the rest of us. When she came home from college for the holidays, he layed all over her every time she sat down. She even took a picture of her laying on her bed on her side with the cat sprawled over her legs in an awkward pose. The rest of us he tolerates. Occasionally he lets me pet him in passing, but really doesn't want to be held.
Here's another thing. I am sure there is a mouse living in my bedroom. The cat sleeps in my bedroom all day. You would think he would at least scare off the mouse, but no. The mouse has full run of the entire upstairs.
So why do I keep the cat? Last night I went to check on my youngest. He was asleep in bed with the cat in a headlock. I pulled his arm off the cat so that the cat could go free. The cat must like him because he just layed there without moving. I'm glad someone is getting some use out of this cat.