It does make sense for extra add-ons / parts sometimes, for things you use occasionally, provided they are already not charging you for the part / add-on (which in this case BMW isn't - they allow you to pay for the heated seats monthly or yearly or purchase it outright). But remember that when you subscribe, you don't own the part / add-on. And if you only plan to use them for 3 months a year, it will not be profitable for them and they will realistically not allow it. Unless it is profitable for them, why would they turn something unnecessarily into a subscription service?