Several month ago many of the cryptos were used as currencies, and mostly bitcoin and Monero.
They were used on the dark web, on marketplaces like alphabay, and before it the Silk Road
http://technews.techfact.org/post/163051106270/the-darknet-marketplace-alphabay-shutdown-andhttp://technews.techfact.org/post/63076057938/silk-road-drug-marketplace-taken-down-and-founderNow with main marketplaces shutdown, these cryptos are behaving more like stocks, which make it difficult to use them as currencies.
Because :
1- Owners will hesitate to use them, for fear of regrets in the future.
2- Businesses will hesitate to accept them due to high fluctuations.