Some points mentioned here like the high level of scam associated to crypto and other factors like not able to trace and retrieve funds when lost are truly retarding crypto from mass adoption. Other vital issues are scalability issues, issue of hacks and meeting up with regulations. We have a long way to go before mass adoption can be met.
In my opinion, the main problems, which are the main obstacles to the widespread adoption of cryptocurrency by states, are that cryptocurrency is relatively anonymous and cannot be controlled by governments. If not for this, states would have long ago legalized cryptocurrencies in their homeland. However, this process has been going on so far and many states are still pondering what to do with it. Its good that the G-7 and European Union states have decided that cryptocurrency does not pose any threat to global financial stability. Therefore, it was simply allowed to be used as an alternative means of payment.