“In 2013, California revised its Zero Emissions Vehicle credit system so that long-range ZEVs that were able to charge 80% in under 15 minutes earned almost twice as many credits as those that didn’t. Overnight, Tesla’s 85 kWh Model S went from earning four credits per vehicle to seven. Moreover, to earn this dramatic increase in credits, Tesla needed to prove to CARB that such rapid refueling events were possible. By demonstrating battery swap on just one vehicle, Tesla nearly doubled the ZEV credits earned by its entire fleet even if none of them actually used the swap capability.”
They sell a tiny amount of cars still, but hit 500k total production last year, which is not insignificant.
If you look at old mobile phones with removable batteries, you'll notice that there is usually a lot of space taken up by the plastic around the battery which is designed to allow a user to replace it repeatedly. A car battery that's rapidly replaceable would need a large, strong structure around it to allow it to be replaced but also to hold together in the event of a crash. If batteries had to be swapped out, you would lose more cabin space and structural rigidity. Then you get to standardised connectors and mountings, data protocols, the list goes on. And that's before you think of the automated equipment to actually swap the batteries.
In a world where we can charge a car today from 10-80% in 10 minutes, it doesn't seem like a worthwhile engineering challenge.