Given the choice would you suggest a person from somewhere such as Venezuela keep their personal savings in Bitcoin or Venezuelan bolívars?
The bitcoin guy is not going to accept 1 Zimbabwe dollar to 1 USD any more than your black market dealer who has USD. The real currency conversion rate is the problem, not the act of obtaining actual hard currency.
yes, there are a lot of fungible ways to transfer hard currency over the internet... once you acquire it.
again: acquiring it is the hard part, because nobody wants to trade a zimbabwe dollar for a USD.
Bitcoin does nothing to help your zimbabwe dollars be less worthless than they are in USD, therefore they don't help the currency conversion process at all.