Most cryptocurrencies are not directly interchangeable with any given nation's currency, and they aren't intended to be. Accepting something like BitCoin as a payment method means Nexus suddenly becomes invested in BitCoin's success and spread, which is a pretty major gamble. Even if Nexus sold crypto as a stock, they would have to accept payment relative to current USD stock market value and then hope that the stock prices either stay the same or increase, which means Nexus could actually lose money by accepting cryptocurrencies. It just isn't worth it right now. The platform already has plenty on it's plate anyway.