Probably because of UX?

At least in the US, the traditional taxis were terrible - only way to order is via phone call, you have no idea when your car will arrive, nor how much your trip will cost, there is no easy way to send feedback to driver, and there was a good chance for an generally unpleasant experience...

Uber/Lyft changed this all and actually made the car-for-hire services usable. In my circles, this was the real reason why everyone simply stopped using taxis completely the moment any alternatives appeared.

And Waymo has a nice app and clean experience, and won't take you long way so it can charge you more, hence people group it with rideshares, despite it technically being closer to taxi.

(I understand that in other countries, taxis were much better. Before Lyft, I always felt envious while reading about their taxi systems)

waymo, uber, lyft, etc. are akin to a classic black cab service where you call a number to make a sort of ride appointment. these never needed taxi licenses, as taxis are specifically hailable from the street at will rather than prebooked.

I think calling them "rideshare" was always a legal euphemism.

"rideshare" means "taxis" now