All currencies of the world (except a very, very few) have been converted to operate through central banks.
It used to be that currency was issued by a nation's treasury, and could be circulated based on the concept of "completed labor" - for example, funding a bridge project as a means to pay the workers with newly created money, which then gets circulated into the economy as they buy things.
Currency is now created by central banks through treasury auctions. These auctions sell bills, bonds, and notes. All of these are liabilities to the citizen - meaning that whoever owns them also owns a claim to the future labor of citizens.
Why do so many ultra-rich keep going instead of retiring extremely comfortably?
Because they aren't necessarily after more money - but the power that it brings. Power can be defined as owning the future labor of other people.
If the lust for power is truly understood then it makes sense why it's wise to have stayed away from cryptocurrencies from the beginning.
I disagree with your assertion that Bankers will never allow cryptocurrencies. I work in cyber security and my customers are almost exclusively banks and other financial institutions. Many have or are making crypto currency plans from accepting, to trading to even creating their own.