Personally I think there are two main barriers:

Pride.- Hard to accept for arrogant people they hadn't had such an idea, hard to accept for arrogant people anyone can tell them about Bitcoin, unless they think you are at their level which is not quite the case in the Bitcoin space; and eventually arrogant people can't accept you have bought cheaper than them, hence they simply don't buy.

Laziness.- People simply doesn't want to make the intellectual effort to understand Bitcoin even at a basic level. That's it.