All the time
Example:
Give driver option to choose accept non cash ride only, cash ride only or both as cash ride carry certain risk, criminals can get prepaid mobile, create dummy email and register as new riders. - Rejected. Reason, impact the reliability of the ride availability (aka riders and Uber fees more important than drivers aka Uber partner feedback). Almost kena, so, even I reached, I decide to cancel the ride. Write to Uber to explain, no cancellation fee, reason, I don't wait for 5 min (wahlau leh, if I wait 5 min, my life and car will be in danger, and I am not Jackie Chan, Ip Man, Steven Seagal, Jean Claude Van Damme or whoever martial art expert)
Told that the current cancellation policy, need to wait 5 minutes only can cancel, or you reach pickup destination, rider cancelled within 5 min, no cancellation fee. Ask to revised. Cannot.
Ride distance is shorter than the distance drove to pick up, which does not make any economical sense nor anyone would do that. Write to Uber, reason given, again, Uber system should be as reliable as possible and available so that riders always get ride whenever needed....
The above 3 example had shown that Uber does not have any interest of the driver at all, all you care is milked as much as possible from the driver! And, how could you say you have assisted your partner, aka Uber driver Anyway, I won't blame you on that, it is rule of the game, business is all about profit, not about charity. But, your actions had borderline of ethical business conduct. Just a friendly reminder to you, there is not only 1 ride sharing service available in Malaysia, there is Grab also.....as much as you can gain ridership share from Grab, you can lost as much driver to them too....end of day, even you got all the riders, but, no drivers....you would still lose....you need to play balance game for both rider and driver. I do not have the data, but, I am sure you have, just go review the active drivers trend...is it increasing or decreasing?

No point having new drivers, but, not active, or just active for short period (to hit the welcome incentive)
I won't say Grab is perfect, they have their own flaws also, but, end of day, given option, riders will choose the best ride from both Grab and Uber, same goes to drivers too, they willl choose the one who reward them the most, or treat them better.....and, how you know, just look at the churned rate of drivers compare to active new drivers rate...now, I had give you free MBA lesson already, no need thank me for that.
yes, i realised that now rider cancel the ride within 5 minutes even if i've reached the pick up location and cancellation fee is not applied. but i've wasted my time, wear and tear and petrol to reach the pick up location to get nothing from it.