Maybe it was a long time ago when Bitcoin isn't popular in the market, but now you can even use it as a payment system like countries that have been declared as legal tender.
I have a lot of things that have been bought with my Bitcoin but it's not directly used in Bitcoin, I converted first into fiat and then use it to buy stuff. Bitcoin in my place isn't yet much popular.
Regarding the black market, I have always been always afraid of making such transactions there using Bitcoin, it's maybe prone to scam.