With menus, everybody gets one and can peruse as they see fit, rather than a little shared computer. With a waiter/waitress you can talk through special options or dealing with split bills and anything like that.
And don't get me started on social and tracking -- I can't think of anything that would more quickly destroy my interest in a restaurant than having to log in with twitter or facebook. (And believe me, if the restaurant posted/tweeted on my friend's behalf, they would lose my business.)