You may look at your bathroom and see a place where you clean yourself, but for you cat, that room is basically a torture chamber. The sink is a slip-and-slide, the toilet is a water bowl that they should DEFINITELY not drink from (they've smelled it, they understand), and the bath they will only be curious about once. Only once.
Check out this week's animation of our favorite senior cat - Earnie - where he discovers the bathroom for the first time. In the battle between Earnie and the water... the water wins.