I think the usual "heated seats" example is a poor one, since it's so obviously an optional feature that not everyone would want to hack around.

Let's say instead that BMW decided all their car models would be physically 4 seaters, but in order to be allowed to use the back two seats, you had to pay a large monthly "sedan fee". And if they caught you using the back seats without paying, they'd sue you. Would anyone accept this? Likely no. And the reason you shouldn't accept this is the same reason you shouldn't accept the "seat heat" fee.