The longer the rider is willing to wait, the more the service can optimize the allocation of drivers. (Less distance driven without a passenger, more distance driven with multiple passengers in a car pool, more direct carpools.) This is a real elimination of waste whose value can be split between the service and the passenger, although it's not clear whether the size of that value is really at the 10-20% level.
If they can pair you up with a drop-off already on the way to your exact location by having you wait a couple minutes, I would estimate this is easily worth 20% to the driver, assuming average trip time is on the order of 10-20 minutes.
