This is a wrong correlation fallacy.
Porn sites, while very cutting edge in a lot of ways (which generates more revenue for them), are extremely slow to adopt changes to their source of revenue because they are very protective about that aspect (for obvious reasons).
Not only that, but the sources of revenue are all deeply intertwined with their affiliate networks, which drive the traffic to the sites in the first place. Shaving is a huge concern, so these sites have to use 'approved' software that everyone else uses for this.
One of the largest used pieces of software is called NATS [1] and it is a trainwreck of complexity. Everything is directed through their integrated billing options [2]... which as you can see is extensive. Why? Because credit card companies will routinely shut down your merchant account randomly... because p0rn.
For the company I worked for (early 2000's), we developed a micro currency that was HUGELY successful and was used for all sorts of interesting things, like pay per minute billing. This was all early/pre days of blockchain adoption and had we used a low cost blockchain of some of this, it might have allowed for earlier more interesting experiments.
Anyway, the full answer is that this is a lot more complex than it appears on the surface and you have no idea what you're talking about here with a comment like that.
[1] https://toomuchmedia.com/pp_nats.htm
[2] https://toomuchmedia.com/pp_nats-billers.htm