I worked for a payment processor in Europe, we provided SEPA and some other payments, but not card payments (so there could be some difference).

Difference is in fees and licenses. Payment processors that process high risk payments (adult industry, gambling, etc...) have higher fees and need license from governing body (usually a national bank in country where the payment processor is registered). So if you process high risk payments as low risk you will get a fine from governing body and you risk to lose your license. And if you don't have a license for high risk payments you cannot process them.

I don't work there anymore, but I heard they lost SEPA license a couple of years ago because of risky transactions.

Now I am not sure if Visa and Master are forcing payment providers to give up high risk transactions or if they are forcing them to classify all transactions as low/high risk.