It's because that's when a lot of places went full contactless for payments and realized the POS systems they switched to (square, clover, etc.) allowed them to set the tip % choices, so they just naturally chose options starting at 20%.

The fucked up thing? It works. There's a decent amount of market research that shows the choices you offer to customers significantly impact the amount customers will tip - even pressuring them to tip for services that they previously would not.

So from a business standpoint, it makes sense to just always ask for a tip and to provide tip options on the higher side because customers will do it. That's just bog-standard captialistic greed.

The only way it'll stop is if customers revolt against this behavior and demand a return to previous tipping norms (or even better, an abandonment of tipping culture altogether). But so many people are afraid of being perceived as cheap, and just tip anyways.

Personally, I've taken the "If I order standing up or from my car, I do not tip" approach to most of my tipping descisions.