The economics completely change with fleet vehicles (aka, self driving taxis). Instead of taking an entire car out of commission for half an hour, you can just replace the battery in 1 minute and keep the car on the road and earning money. Because both the car and battery swap station is owned by the same company, there's no arbitrage between trading an old, worn out battery and a new battery and fleet cars can be designed alongside the swap station to make the entire process entirely automated.

But the big plus is that if you design a fleet system around battery swap, you can get away with puny batteries on the vehicles. A battery sufficient for 1 - 2 hours of city driving is optimal which saves both cost and weight for the vehicles. Instead of relying on expensive, power dense advanced Lithium batteries, you can shove cheap batteries into the thing, scatter the entire city with drive-thru swap stations and drive the cost of transportation way down.