The stressful and annoying payment dance at the end of a cab ride was a not-insignificant factor in the rise of ridesharing.

Why should employers pay employees when their customers can do it for them?

Or so I was told. I saw it more when I was younger than I do today.

Generally, most tipping is at restaurants and bars/pubs. Hairdresses/barbers/salons is also very common because of the close personal interaction with the worker.

Most of the time you tip at businesses that would be expected to employ low-education, or poorer or immigrant workers (and by extension, more easily abused workers.) Restaurants, salons, car washes, etc, all tend to employ poorer, less educated people, and also tend to be highly tip-based businesses. So for the most part you're expected to tip at businesses that traditionally abuse and underpay their employees.

But in the USA, it is not uncommon to see Budlight selling for 8 dollars or more. (don't forget to tip!)

If they weren't using the same currency there would probably be difference in inflation due to very different economics between let's say New York and some tiny rural village.

Really? I never know anyone doing this

In the US, yes.

People I regularly tip: - wait staff - barber - delivery service (for oversized packages/furniture delivered into my home, not general UPS/FedEx deliveries that are left on the doorstep) - taxi driver

It's a side effect of a low minimum wage. Most of the rest of the western world has the minimum set closer to a living wage.

But why taxi drivers? Why delivery drivers? Are those groups also poorly paid because they rely on tips? Why other social groups haven't adopted this? Are your electricians also charging $1 an hour of work and then expect that you leave a tip that saves them from poverty?