Once a chargeback is filed you are losing the fee if you either accept it or don't fight it. My cancellation process is simple, certainly simpler than contacting your bank and identifying yourself and going through the chargeback process. That doesn't stop people from going to their bank for the last 3 months of subscription and calling them fraudulent because they never told us to cancel them. I fight every single chargeback because their always lies by the customer in my case and they involve real money already spent by my company. We win some and lose some.
But you're absolutely right. If it were physical goods or services, I'd fight those chargebacks for sure. (Though it'd be a lot harder for one of my deadbeat customers to plausibly claim that he'd "forgot that I mowed his lawn").