Restaurant owners love it because it hides costs from customers and allows lower pay for workers (it does do both of these things very well).
Workers "prefer" it because they have stockholm syndrome'd themselves into thinking that drawing a smiley face on receipts will get them higher pay (it won't.)
Once that became a thing, yeah, a lot of other places took advantage of it. It wasn't hard to turn on the tipping feature on your payment processor, so they did -- even if the reasoning was much less clear.
And of course it's a ratchet. Nobody turns it off even as the pandemic normalizes.
I guess as long as even some small portion of the population always tips when the option is presented- they don't really have an incentive to turn it off. Like rejecting free money when your competitors aren't. I think for any reasonable attempt to stop these kinds of practices it really has to be stigmatized on the cultural level for people to feel some revulsion when asked for a tip in an inappropriate situation. If there was no option on the processor they'd probably just leave out a tip jar or continue to ask for it in an awkward and roundabout way ie hanging around waiting for you to get some cash out after the transaction is complete.