I don't know what you're referring to here. In most countries it is perfectly legal to pay for most goods with Bitcoin, and governments and legislatures have already regulated it, so it's not "because they don't know". So technically this "barrier" in most countries (except some dictatorships like Turkey) doesn't exist.
Yes, it is allowed in most countries, but not officially. The government did not announce that its legal tender. If a certain kind of paper today gets some value worth more than the dollar, and people start accepting it as a medium of payment, the government might not object, but they won't make it legal tender. The government can't make it illegal because it's a free country, and also because they're not committing any crime by using it, except in a dictatorship, like you said. As long as the person accepts it for payment, it's his business. It is regulated and free to use, but it doesn't mean it can creatively destroy its predecessors because the government won't let it. That is what I mean.
So, the government in this context is the barrier. If both fiat currencies and Bitcoin were currencies not printed, controlled and backed by the government or state, Bitcoin would become the leading currency of the world in terms of usage for transactions. So my point is, the government is what will not allow Bitcoin to "creatively destroy" fiat.
