“‘tipping is mandatory’ — any idea how that works?”

photo by Rukasu1

“Dear PoPville,

At the nationals park the other week, I bought a beer from someone walking up and down the stands and was given the option of tipping 15, 20, or 25%. Later, I bought a second beer from someone at a concession stand and was told that “tipping is mandatory” — any idea how that works? I’m happy to tip, it just feels strange to mandate it and then call it a tip”