On the one hand I agree with your argument. On the other, it's the reason why a lot of the US has poor internet speeds. Maybe "a company can continue to be profitable" isn't sufficient. I think the consumer impact/benefit needs to be considered as well. I wouldn't argue turning off FM provides much consumer benefit though.
In market economies, consumer impact/benefit is generally what determines whether a company can continue to be profitable. If there's no benefit, customers won't pay, so there's no profit. The thing to remember, however, when it comes to commercial radio, is who the "customer" actually is (hint: it's not the person listening to the radio, unless it's a subscription service like SiriusXM).