It's ideal really; those who can buy new eat the depreciation, while those who can't afford new end up with a vehicle that will be able to go hundreds of thousands of miles before end of service life (perhaps with some cosmetic blemishes, but not much more of concern considering powertrain longevity). Not everyone needs a new car, many simply need a reliable car.
Consider: I had my last car purchase (which I knew would be used) between a BMW 4 Series, a VW Golf R, and a Subaru STI. I went with the 4 Series. The Golf R and STI are often used as track cars, and 40k miles on a Golf R may very well be the equivalent of 100k miles on a regular Golf.
I admit this is a very specific use case, but there are other specific use cases (e.g. police car - probably spent 80% of its engine's life idling and not racking up miles) that we know to look for, that we simply don't know to look for in the EV market, because they haven't presented themselves yet.
But yes: batteries age and need to be replaced. But while that's quite expensive in materials, it's actually very feasible as a maintenance task. A 2012 Model S could have its battery swapped and no doubt drive for another decade with minimal fuss.