I think this is the biggest problem with cryptocurrencies. Reversible and traceable transactions are a feature of real money, not a bug.
That depends. Having a paper trail of your money in local tax office sometimes means you would be shot in a head and buried in a nearest forest.
When armed insurgency happens (and yes, they do happen) all you see in the news is "Country A" occupied parts of "Country B", but on the ground you would have armed people going full-DAESH on local tax offices to see whom to demand ransom from and that would be law-obeying people with paper trail for their earnings.
Looking at the big picture, this is even worse: the way you don’t have Daesh is by having a strong society which has the resources to fight them off. A society with rampant corruption and black market activity is exactly how you create the conditions for them to thrive!
No, I just forgot cash existed for a second.
For example I can accept my earned money on account in Ukraine, pay taxes here, but can't send it back to an investment account somewhere EU. This just can't be done.
Even more sillier - some time ago it was illegal to merely have an account in foreign bank without obtaining personal license from central bank here.
So yes, there are cheaper ways and there are simpler things and there was people who were sent to GULAG for doing "illegal money transactions".