My wife and I were at a restaurant (more sports bar) in Houston and when the check came, I pulled out the credit card and was told "oh, our machine's broken." Since I was working in the treasury group at my former employer at the time, I pointed out she can do it manually it over the phone. The waitress said she couldn't do that either.

So I told her "I don't know how much cash we have and I doubt there's enough for a tip" she said "that's OK, as long as you can pay the bill". We scraped together what we had and she probably got a $.50 tip.

Unsurprisingly, the place shut down about a month later.