What tipped me over the edge on my acceptance of tipping culture, was seeing a tip screen pop up on a display after paying at what was essentially a local fast-

What tipped me over the edge on my acceptance of tipping culture, was seeing a tip screen pop up on a display after paying at what was essentially a local fast-food place. What service am I tipping here for? That I liked the 1 minute I talked to worker? When I was younger, It made sense to me to tip housekeeping if you make a small ask of them, or to tip a service worker if you make a request outside the norm; you're asking more of them than most people after all, and you want to add some grease. But what is with tipping for doing the standard of exchanging money for goods and services?