Why is it important that you tip?  It's not as if a scam could be kept a secret because when the gratuity is rolled into the price of the food *everybody* on the staff will know just how much money is coming in from each table, and if the restaurant starts skimming it will get reported to everybody who has an available ear.

It's better than the current system where a customer who's had a bad day just walks out without tipping and leaves the server on the hook for taxes on that tip they never received.