I can understand someone leasing the entire car, battery included.

And I can understand someone buying a car outright.

What I can't understand is why someone would want to buy a car outright, but still end up paying a lease on the battery. To me, that doesn't have the benefits of either option.

People have been worried about EV's batteries in terms of lifespan, loss of charge, maintenance, etc. The option to lease the battery was a way to alleviate that worry, IMO.

That's true but you can always lease the entire car. If you only lease the battery you can't just let the lease expire because you still have to find a new owner for the car and if the car has a reputation of needing battery replacements then you might have trouble finding a buyer.

It didn’t add up economically for my wife’s car.