I have ever seen a waiter chase anyone else. But once, a bit drunk and splitting a check with a friend (but me doing all the math), we shorted the waiter and only have a 10% tip. He very politely approached before we left and asked if he'd done something wrong. I said no and asked why he asked. He said "well usually people tip at least 18%..." and I was mortified of my own error, I assured him all was good and we each doubled our tip to leave him 20% - which is what we'd intended on giving him!
In some states waitstaff are paid minimum wage but not in most. And honestly... its extraordinarily difficult to live on minimum wage even if is what someone is paid. Usually a standard 40 hour week is not going to cut it, and people on minimum wage almost never have things like paid sick days or paid vacation time, or particularly good health insurance, etc, so not only are they making very little they are in more need of savings as a safety cushion.
The way I look at it is - no one needs the luxury of being waited on. One can go to a grocery store, or even a self-service eatery, to get the food necessary for life. Going to a restaurant with table service is a luxury, a small one but a luxury none the less, and its awfully stingy to be cheap about tipping when you are already engaging in luxury behavior.