Yes, I pay with credit card 9/10 times and get a receipt. I doubt any of these companies are big enough to have offshore companies to route their income through.

"Then why not just let them compete?"

They do. There's quite big competition in my city among public transport (city owned), many local taxi companies, private taxi drivers and Uber. Competition is quite fierce and costumers can choose freely whatever they prefer. I prefer taxi, I call taxi, some of my friends prefer Uber - they call Uber. What other competition do you have in mind?

You can exercise your opinion by not taking an Uber. Why would you ban a third person from using uber?

The competition you describe is exactly what's needed, but that's not always the competition that's allowed.