On the Internet, you can already pay with cryptocurrency, not everywhere of course, but the list of available places is constantly growing, but there is no normal access to the real market yet, business is not interested
The reason why adoption is slow is because of the price volatility. Major economic players once met to stabilize world currencies and were successful. Thus ushering in a world that is the most interconnected in modern times.
I believe cryptocurrencies will also do the same thing in the future. However that doesn't stop payments and remittance projects to try using blockchain tech. EthaRemit.org has been testing solutions to that end.