The problem with any way of hiding value for a mighty state that wants to take it away is of course that stuff is valuable mainly in interaction with others.   The only value you can truly hide is knowledge, as long as you keep it for yourself.  As most value is created in economic interactions, the weak point of failure is exactly that you have to interact with others, who can betray you.  Most hackers know that "social engineering" is way way more effective and valuable than pouring over thousands of lines of code to find a hole.  

So as long as mighty states want your value, you run a risk if you have to interact with others on that value.  This is a problem that monero cannot solve of course.  If you've sold a service (say, homework help) to someone else who paid you in monero, then that person can always betray you to the state and that state can come after you to take away 2/3 of the value you provided (called "taxes"), with a punishment on top of it because you didn't give it to them right away.

Of course, all bets are off if you use centralized services.  That's a gold mine for states.  

It is only in this (admittedly risky) endeavour to try to hide economic activity from the sticky fingers of the state, that I see any reason for crypto to exist.  I fail to see any other use case that isn't covered better with fiat-like systems.  But, as I said, it remains a risky business, only open for those people who love liberty more than comfort, and willing to take huge risks of others betraying them.  And as we can see, there aren't many around.  So most probably, this project (crypto currencies) failed and is on the verge of becoming a weapon in the hands of big bad evil states instead of a tool to fight them, especially transparent crypto.