> They don't have forbidden business lists just because they don't like pornography or sex toys.
Those are "high-risk" mainly because of "reputational risk", not because of chargebacks. Which I imagine is code for Visa or the banks thinking "If too many people with traditional morals get into political office, they'll start cracking down on us if we do business with the sex toy companies." https://en.wikipedia.org/wiki/Operation_Choke_Point
There's also some bad history with old porn sites, since they used 0-days to install dialers on people's computers to rack up tons of money when they used their dialup to connect to the internet. Hence the old "I think my computer has a virus", "Quit browsing those weird porn sites" retort you may have heard. They did other shady things which got Visa in a bit of trouble. It doesn't happen much anymore, but I suspect the organizational scars remain.
You've insinuated that pornography or sex toys are often "forbidden" because they have a high chargeback rate. But if you have 0 chargebacks after a few years, you still won't be able to negotiate a lower rate or to use a service like Paypal or Stripe. Because chargebacks aren't the reason.
Visa and MasterCard charge you $500/year each as an extra fee too, so I suspect the Stripes and Paypals of the world can't combine them into their aggregate account. A fee like that would seem to preclude even a specialized aggregate account, without a special agreement with Visa.
Also, if chargebacks were the issue, I would expect companies that only take debit cards to be in a different risk category than those that take credit cards. Debit cards have reduced fraud protection, so a Paypal or Stripe's underwriting should be more lenient for them. But I've never heard of Stripe letting you sell porn or of Visa waiving the fee if you only take debit cards. It could just be uncommon though.
Plus, I believe both Paypal and Stripe ban selling porn even using e-checks, which is more evidence against chargebacks being the issue. There shouldn't be any restrictions on the ACH system, and even if there usually were somebody could set up a state credit union in Oregon or similar to handle it.