[frankreyes]

The difference is temporal: tip is for a "past" already rendered product or service. Sbf, Holmes, et al, it's about a promise for "future" services, which have a risk associated of no delivery or render. When you've already eaten your burger there was no risk of uncertain delivery. The causal relationship is reversed

[sixstringtheory]

True generally, but it gets murkier all the time. Just last week I ate at a traditional restaurant that stated up front that there is a 15% service charge on all checks. This was in a city that has a very high minimum wage even for tipped employees. More traditionally, parties of a certain size at a restaurant always are charged a fixed gratuity.

Then there’re the square terminals that are normalizing up-front tipping for everything, not even just food service anymore. I’m sure I’m not the only person who has tipped up front for something and the service wound up being terrible. So there are three examples of tipping towards the future.

There’s another future component to tipping: in many places there is regulation that states if the tips don’t make up the prevailing normal minimum wage, the employer must pay the difference in salary. I’ve personally never seen this happen and I worked for tips for about 7 years.