The big issue in Europe is that there are a plethora of low-cost instant and risk-free payment methods already in place.

For example;
- Spending 300 euro on a credit card costs less than 0.2%, and most transactions are not subject to fraud due to 3D secure (online) or chip and pin (point of sale).
- I paid for my coffee this morning (3.65 euro) via a contactless card which cost the merchant about 4 cents to process (due to being contactless).
- Even for those without cards inter-country bank transfers are generally free and often instant.
- For those who love anonymity there are tens of millions in anonymised payments transaction monthly via PaySafeCard, Ticket Surf, and others.

...as a payment method, it just doesn't have a use case at the moment (other than darknet retail).

As a store of value in Europe, sure. However it is still inflationary and volatile, and people have low cost access to other inflation proof investments. Again, no real use case (other than hiding wealth effectively).