There is a logical explanation for this.
First, the volatility inherent in digital assets. The fact is that the main goal of every bank is to make a profit. The slightest fluctuation in the cryptocurrency market increases the risk of reducing all projected profits to zero. Today, cryptocurrency is showing a certain stability, but even despite these indicators, most financial institutions still prefer to provide traditional banking services for corporate clients, whose activities they understand.
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I believe the quoted above is the main reason why banks are feeling very reluctant to accept crypto, banks are set up for profit making, almost all banking transactions must involve them taking interest or commission, if crypto with the high volatility will prevent bank from making that profit, i don't think they will be interested in working with crypto, at least not anytime soon.