Is it true that Uber Scheduled Rides are not guaranteed?
The Guru Take
Correct. They are not guaranteed.
That is correct. The "Scheduled Rides" of Uber or Lyft are not guaranteed. This is due to the on-demand nature of their drivers. There is no way to be 100% sure whether there will be ample drivers and vehicles for your pick-up location in advance. This is from Uber's website:
Q: Am I guaranteed to get a ride?
A: Uber actively monitors availability to ensure that a car will arrive during the period you schedule a ride, but does not guarantee your scheduled ride. In the rare case a car cannot be found, you’ll be notified immediately.
This tells us how their scheduling system works. It basically sets a reminder in their system to automatically "dispatch" a car for you 10~30 minutes before a specified time. The rest is basically the same Uber and Lyft. It offers the fare to a driver nearby, he or she accepts, and comes to get you.
BTW, Lyft has a nice feature where they show you the price in advance as well, and they anticipate the Prime Time (their surge pricing) and lock it for you. No surprises.