They get pissy if they don't get the normal tip, but I agree, they don't earn it anymore than a McDonald's employee.

What you DO need to consider: Server's taxes are based on the cost of the meal, not the amount tipped. For example, if the bill is $100, in Michigan, they will take 8%, or $8 for taxes, even if no tip was left (some servers actually do get negative checks, owing the restaurant). So, for carside, you should tip at least $8 in this very expensive takout meal rather than the usual $15.

* Prices chosen for obvious math.

Find out what your state charges servers for income tax.