I assume this is why OF has not integrated crypto pay-ins/pay-outs. Their users want a quick wank, not a 3 hours deep dive in crypto.
I don't know if that's the reason though, since integrating payments with BTC or ETH is relatively easy. I'm guessing it's mostly about regulations, and also because it's a subscription service and they might want to keep charging that card every month.
There are many sites in the adult industry that allow payments with crypto, such as LiveJasmin (owned by another Hungarian btw).
But you maybe right about the user base. It's probably teenage/college kids that get to the OF profile of a particular girl after seeing a TikTok video, and then they use their parents card or the card they have for their college expenses.