I dont think this is a stance taken by the banking industry, as such. Credit card companies take payments from almost every porn site on the internet.
I believe they aren't prepared to support OnlyFans because of the fraud risk. The website has refused to set up a system to offer refunds to customers who pat for something they don't receive. Apparently it's rife.
It's likely one of the replacements for OnlyFans will be JustForFans, the creator of which stands accused of multiple instances of rape.