Also, relaxing. Having a dependent of any kind sleeping soundly close to you implies safety and reassurance in a very primal and satisfying way.
And cats sleep far more than humans do. Even when they're not active they're nice to have around.
I'm not convinced by the "tamed predator" hypothesis. I think if it were true we'd consider them exciting but stressful - like crime fiction.
Clearly we don't. No one sleeps next to a violent crime novel for relaxation.
In fact cat owners often get cognitive dissonance when Furry McPurrFace goes out and eviscerates a bird for breakfast. We feel sorry for the bird, but we don't seriously think "That could have been me. Or one of the kids."
