The majority of porn websites are totally free and offer a wide range of options for the visitor without demanding any payment. This may seem weird, because they obviously have to make money somehow. But in fact, porn platforms make money by placing ads on their website. They get thousands of visitors each month, and are therefore very attractive for advertising different porn and sex-related products.
Taking this into consideration, it then becomes unclear why one should bother buying a subscription on a website that offers tons of porn videos, for free. And still, most porn websites do offer the option of subscription. And there are many people who actually pay for subscriptions, especially on such well-known porn sites as Pornhub, Brazzers, etc.