When you consider that $10 per day per person is for service for at least three meals a day, cleaning the room, evening turndown service etc. it really isn't that much, IMO.
I recall when some cruise lines suggested half the customary tipping amount for children I always thought the kids probably caused more work than the adults!
Plus, some of the autotip amount also goes to "behind the scenes" workers who contribute to your cruise enjoyment even though you may never see them. Currently cruising is one of the bigger travel bargains around for the value received - even when you add in the tips.