Toilets go in toilet rooms, not bathrooms.
Putting a toilet in the bathroom would mean the bathroom could wind up smelly when you want to take a bath, and would make it difficult for people to use the toilet when someone's soaking in the bath.
Not to mention the bathroom floor will frequently be wet from the overspill from the tub, so you don't really want to walk in there when you're not going to bathe.
I hear there do exist some weird foreign cultures where they put toilets in bathrooms, though.
