Back in the golden age of the internet*, that's pretty much how it used to be.
* After the days of slow dialup yet before all the Current Year enshittification.
Back when people could make respectable money from a couple of unobtrusive text-only Google Adsense banners on their blogs. Unfortunately bandwidth speeds were always going to increase and the spectre of the phone poster was already on the horizon.
The unit economics of cloud AI are very different from traditional Software as a Service. If you're running, I dunno, a forum where people can use it for free or pay to get a special banner, additional reaction stickers and a private board, each individual user (free or paid) isn't going to add anything noticeable to your running costs unless they're DoSing the site or something (and then you ban them for abuse). So free and premium features can be kind of arbitrary and a premium user doesn't really have to cost you more than a free user, depending how you structure things. Your running costs are mostly overheads rather than unit costs and additional users are marginal. Each user action is also marginal, so heavy users don't cost much more than inactive users. So a few premium users can effectively subsidize a much larger number of free users.
With an AI generation service, every time any user uses the core functionality of your website, there is an exact dollar charge on the API you're wrapping or the cloud GPU minutes you're using. If you have your own hardware the cost is less direct, but you can still only run so many generations at a time and the limits bite far quicker than they would on a traditional service because each user is doing something computation-heavy rather than just reading and writing a database. With traditional SaaS you're slapping an entrance charge on a bar, but with AI generation you're selling drinks.
So maybe you can afford to give away a few free generations to entice people to pay for more. In any case, free users are a calculated loss and premium users are an ongoing expense. Heavier users cost you more in a very legible way, hence most of these platforms have usage limits and credit systems. This is very different from traditional SaaS, where the cost of each additional user is usually marginal, doesn't change much based on their usage of the platform, and premium users don't cost significantly more than free users.
If you've got tons of money to burn and you want user data to train your own models, like OpenAI, Anthropic, Google (who also owns their hardware), etc, you can afford to take the hit to a greater or lesser extent (notice how Anthropic has very severe free tier limits vs how Google runs inference on free searches). But smaller platforms that don't train their own models don't really have much incentive to let you spend their money for free.
A site TOS may not be binding though (and I really dislike when they try to rule out Fair Use). But I'm pretty sure that hacking to get around paywalls isn't really legal...
Many paywalls can be defeated by disabling JavaScript, or visiting the article from a search engine instead of directly. It's hardly what I'd call hacking, though the courts may have a different view.