That looks like a good point.Well, this is true for any business.
No. A tip is an incentive to provide good service as well as a reward for doing so. Inserting it into the price of the meal would reward poor service, too, and is no longer a tip but the price of the meal.
Why don't we do like that in other places? There are laws, protecting consumers, providers, etc.
An intervention into the natural human activity.