The only way people would pay for web sites in the extent they pay for apps is if it’s as convenient. I don’t want to log in to get the paid benefits for example. I don’t want to enter my cc details to pay the subscription if it could be avoided by “the store” already knowing it, and so on.

In the end reality is that I just pass on buying subscriptions and would probably prefer buying subscriber access to a website if they made an app facade for the site that handled payment and login. The UX of web sites and subscriptions is that bad.