In places like UT and TX, waiters get 2.13/hr. The only reason they are there serving you is because it's expected that you'll tip, and you know that. If you're not going to, whatever, but tell them beforehand so that they can give you service that reflects the 0 dollars they make from giving it.
That said, this is strictly for sit down restaurants. I'm as puzzled by solicitation to tip the counter person et al in fast casual places as the rest of you.