There is a reason taxis are painted particular colors (color scheme) with giant numbers visible from a distance, medallion clearly displayed, taxi light, meter, cc machine, big required stickers, etc. so even drunks can realize it’s really a cab.
Anyone can make a xerox of an Uber symbol and put it in their back windowed their car.
It would be far more difficult and expensive to make your car look like a taxi. Also the other cabbies in town would quickly turn you in as a fake cab.
Again, the apps clearly show the make, model, color and license plate number of the car that will pick a passenger up. I just used Uber yesterday evening at SFO to get home to the South Bay - black Toyota Prius, license plate number and driver name were all shown in the app and that’s what I looked for, in the midst of lots of other Uber and Lyft cars picking people up at the international terminal. If anything, you get much better traceability with the ride-sharing apps than with taxis.