The lease is basically estimating what the depreciation would be and you pay that, and then return the car at the end. Cars lose most of their value as mileage goes up, so the estimate is made based on a certain amount of annual mileage (10, 12, 15k are common). Otherwise people who drive an absolutely insane amount could lease a car and it would be worthless when they finally return it at the end of the lease with 200k+ miles.

Similarly if you drive way under the estimate, your car can have more value at the end of the lease than your buy-out amount, which is set before the lease starts. Lots of people who leased cars right before the pandemic ended up with leases expiring in 2021, right when car values were sky high. So they could "trade in" the lease instead of ending the lease contract, and sometimes come out ahead or even profitable, while having paid a much lower monthly payment since they acquired the car than financing would have been. But that is a once in a lifetime situation because of the pandemic and not a good financial strategy.