You aren't paying for usage, you are paying for the product that the subscription is offered to. If you are paying for usage, well, that's their billed by token-usage API plan, which they are quite happy for you to use with any client you want.
Even worse, if I'm paying a subscription for the product, and I don't want to use the product, what's it to them?
Even worse, if I'm paying a subscription for the product, and I don't want to use the product, what's it to them?