@docpop A first order estimate of the number of cars going to pick up people is the number of cars with passengers.

But even doubling the number of passenger-initiated relocations would still keep "productive" moves below 10%.

Of course, there are other reasons to continue driving besides the parking fees: 1. Acquiring more training data; 2. improving the statistics: Distance driven, distance without accident, …
But there should be disincentives of clogging the streets during rush hour.