Why do people give tips at Yogurt Land?

I honestly don't give tips, since it is a serve yourself kind of place.
Answers

Erik

Most people don't. But I'm sure they pay those people next to nothing. It's a way for management to give them more, without having to reach into their own pocket.

Bob

You don't have to give them a tip if you don't want to,and while I have never been to yogurt land, it sounds like a fast food kind of place and at some of them, like Subway for example they have a tip jar.