Some banks and corporations said theyre halting purchases of Bitcoin and other cryptocurrencies on their credit cards. Banning it because they dont want the credit risk associated with the transactions. Some says that allowing purchases of cryptocurrencies can create big headaches for lenders, which can be left on the hook if a borrower bets wrong and cant repay.
The reason why the banking system wont allow people to purchase crypto currency through credit is simply because it is volatile and if people start investing in it and if they are not able to repay because the price went down would be a disaster everyone is curious about and so is the reason they are implementing these sort of things and that does not mean that they are banned.