You don't need a logical reason to justify tipping
Well, I guess you learn something new every day. But I never thought tipping was racist. That, however, is the claim of one American burger joint owner who is banning customers from leaving tips in any of his Shake Shack premises.
He says that this is because of slavery and claims tipping stems from a time when black waiting staff weren't paid for their labour, but allowing them to collect tips was a handy way of saying they weren't slaves.
That's an undeniably fascinating historical nugget, but it bears no relation to the real world. After all, tipping goes back to the London coffee houses of the 17th Century.