That's because the bank has liabilities / duties to the country it operates in and a registered exchange (company) is an easy / no headache source of funds for them, right?
The banks just tries to cover their asses, especially after the huge fines they've had recently for not doing enough against money laundering. Even though, as far as I know, those fines were based on fiat money laundering.
That was my impression, too. So it means if politicians one day find out that criminals use centralized exchanges as well, cashing out via centralized exchange won't be any better than P2P or decentralized, right?
It seems to me like you need some sort of 'government-approved party' in your crypto-to-fiat-path to prevent issues. What if new exchanges are based in crypto-friendly country like Portugal or El Salvador; such an exchange could probably get away with accepting all UTXOs, without blacklisting, while at the same time being 'governmentally-approved' so that banks won't need to thoroughly question source of funds when cashing out.