Bitcoin isn’t really used much as a currency at all.
When people buy bitcoin, they rarely use it to buy goods and services. They’re really buying access to a Ponzi scheme.
I subscribe to this school of thought. Bitcoin is probably a good idea as a currency. Problem is, people don’t exchange their dollars for Bitcoin and use it to buy goods and services. Instead, they buy it in the hopes that other people will hop on the bandwagon, and cash-in on its price appreciation.
The same thing applies to other Cryptocurrencies.