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?
The most basic reason is that this sphere is not regulated in any way and is not recognized by most countries. I think that this process will accelerate as soon as at least one of the influential countries recognizes the crypto currency. And while this industry is between legal and illegal, then we will not see a mass application.