I know plenty of Uber (and normal taxis) drivers around the airport here who pick up a someone, then ask if they mind taking someone else. Because it is usually vans and business customers, they don't care and actually kind of like talking with other business guys who probably went or are going to the same seminar/conference etc. The driver will then load up whatever fits who are waiting for taxis or drivers and only report 1 person to the service. As this is hotel to airport to hotel, there are not many ways of uber, lyft etc detecting this unless someone rats them out. I asked a driver and obviously he responded with Uber screws me, I screw Uber.
In Vietnam, if you see a parked driver waiting for a call, you can show him your Grab (ie, Asian copy of Uber) price to go somewhere, then get the same ride for 80%.
A similar thing happened to me in South America while on vacation, I was looking to book an Uber but the taxi driver gave me a small discount to do it "on the side" and explained that he wouldn't see most of the money from Uber.
As a passenger, the advantage of Uber is that if something happens, I have someone accountable: drive + car plate. But in reality I don't know if that works
Many normal taxis drive also for Uber or Lyft as you need the license anyway over here. Not sure if you can be Uber AND Lyft at the same time.
Payment is preferably cash (I started wearing cash again with how the lovely cashless stuff is ramping up here in the EU), but I had all drivers so far who simply had this Square like device on their phone to take payments. So the driver runs around to let out the 'main' passenger, let's them walk off, runs around to open the van door and tell what the price is cash or tap your card. That is the most common. I see sometimes they charge similar to what the 'main passenger' pays and sometimes less.
