They can't, crypto isn't a stable asset it's highly volatility and far different from money, it's going to be hard to see crypto and medium of exchange really because the volatile part doesn't guarantee anything
In all, I believe that is the major issue cryptocurrencies have when it comes to seeing it as a means of exchange and on a positive note, why people are more into crypto. If there was no volatility in crypto, there wouldn't be the king of profits that investors get from it and wouldn't have been investing in it that much. So, what is a positive for crypto investors is what makes it difficult as a means for exchange hence, it is different from money.