dishwashers are fine unless you are totally fanatical about cleanliness, in which case you'd be better off hiring a maidservant. But even if you've got one you still need a sink, unless you use nothing but crockery and cutlery in your kitchen. Where would you wash out a paintbrush, for instance? If you normally do that sort of thing in the bathroom basin, fine; but it might be worth drawing up a list of exactly how you use your sink now, and whether it could all still be done with a smaller one.
And don't tiddle in it, it isn't done.