Question: If it's mandatory, HOW IS THAT A "GRATUITY" IN THE VERY SENSE OF THE WORD?
Waffle House does this for to-go orders. If you didn't partake in their service, it's even stranger to call it "gratuity."
didn't partake? Did someone who works there take your order? then take it to the cook? then get it when it's ready? and ask you if you needed anything as you were picking it up to go? Aside from sitting at a booth and getting a glass of something to drink, and them stopping by twice for 10 seconds to ask if everything's okay. The take out order is exactly the same, you tip less because they don't have to spend the extra 30 seconds re-filling your drink. But nothing else is different. So I would say a to go order you're definitely partaking in their service and using a server to do it. Unless a robot answers your call, takes your order and gets it for you auto magically.
Tipping for crappy service sucks, but everywhere I eat has signs posted everywhere saying parties of 6 or more get a automatic gratuity added to their bill. I don't see how anyone could possibly fight this and win. It's posted, if you don't like it go somewhere that doesn't automatically add it. Chuck-E-Cheese is about the only place I can think of that doesn't though.
BTW - At least in California, a mandatory addition for parties of 6 or more is definitely legal. They consider it a legal binding agreement because it's posted for everyone to read, and by eating there in a group of 6 or more you're agreeing to the conditions posted. It might very in other states I dunno.