I don’t begrudge the OP; he made a cultural gaffe. It’s as simple as that. Know that he’s been properly educated, he’ll know better. We can move on now.
I usually tip a minimum of 15% even if I’m angry at the service, but most places I’ve been to the service itself is usually “Meh, okay”. I usually tip 20% or more if I’m at a bar, and there I can see how well the bartenders are working behind the counter. Even if I have to wait because it’s busy, I don’t mind as long as the bartenders are working and not sitting around talking to each other. But if I see some guy sitting around, playing on his smart phone, and not serving, the tip goes down. I have all the evidence I need. Even then, he’ll still probably get 15% - he shouldn’t, but he will. If it happens enough, I just don’t come back to the place for a while.
And that brings me to my next point, which is that restaurant service is a team sport. What businesses and their employees ultimately want and need are satisfied customers. You can call me cheap - that insult won’t bother me. I’m not petty, but I’m frugal and I don’t have to eat out at a restaurant. And I certainly don’t have to eat at a specific restaurant. I don’t want to hear from some waiter, either in a restaurant or even online, about how hard waiters have it. A lot of people have difficult jobs and don’t get tipped, including service workers who get paid minimum wage. I appreciate the jobs that waiters do and I doubt I could do it well, but that could be said of many people in a variety of jobs. Wait staff aren’t special.