The global economy is nearly 80 trillion USD per year. Payments using any type of cryptocurrency as a medium of payment is a tiny fraction of this total.
What are some of the reasons preventing cryptocurrency from being more successful as a medium of payment?
It is actually the start of the cryptocurrencies that is why you are seeing like this and even in the start you can see that how much faster the process of adoption is going. The cryptocurrency itself is being used as asset too by the traders which make the price of it fluctuating which also made the process a little slower but that is not a hurdle it will spread all over the world as payment sooner.
So, an obstacle is cryptocurrencies are used as store of value, like a security, instead of a method of payment, which is an attribute of a currency. The result is because it is a security there is a lot of price volatility. Price volatility makes it difficult to act as a method of payment.
This is another "Catch 22 Problem" in that until there is widespread use of cryptocurrencies as medium of payment it will largely be a security, which means price volatility. Price volatility is an obstacle to adoption as a method of payment.