I hate how there are all sorts of random situations where I'm expected to tip. I've been told I'm supposed to tip at the car wash, when getting a tattoo, or using a food runner (do I tip the UPS driver?) - it's all senseless.and strikes me as a money grab against good natured folks.

The US can be really crazy. Part of the issue is that you have to understand compensation models--for example, my understanding is that like waiters, delivery drivers largely work for tips (usually). But, especially when traveling, there are a gazillion situations where a dollar here or a dollar there seems to be routinely expected sometimes. I suspect that I don't leave tips in some situations where many people do. (No, I don't routinely leave a few dollars a night for my hotel room servicing.)

No to UPS driver. Tattoo? No idea but probably given that I tip my barber.

In China, you're not expected to tip at restaurants, and you'll confuse people if you try.

You are, however, expected to tip your doctor before getting surgery.