A sheep will never sue you for palimony. A sheep won't care if you screw her sister. A sheep won't care if your secretary is better looking than she is. A sheep will never tell you the ceiling needs to be painted while you're screwing. A sheep won't use your razor to shave its legs, or your pocketknife to open a paint can.
Sheep never have a headache.
A sheep won't give your favorite hunting shirt to Goodwill. A sheep won't leave wet nylons hanging all over the bathroom. A sheep will never ask you to stop on the way home from work and pick up a box of tampons. Sheep grow their own fur coats. A sheep will never leave a vibrator on the living room couch when you're having friends over to watch football.