Yeah exactly, That buyer himself/herself can scam you lmao. And besides, I don't think there's something wrong in asking for a tip. I mean, don't some Uber drivers and other such service providers ask for a 5-sstar review? Similarly, I don't think requesting for a tip is WRONG, it's just that it shouldn't be forceful, but rather the buyer's own wish.
And, the tips we pay to Waiters, Cab Drivers etc. go DIRECTLY and COMPLETELY to the individual and the company/restaurant management have no right to take any part of it I believe. Thoughts?