Completely misunderstood assumption I believe. First things first: bitcoin has not accomplished main stream adoption as of now so we can not really Call it “main money system”. I think that’s what you trying to say with just different terminology.

For bitcoin to be accepted throughout world needs some sort of regularities. Like every place I go there should be peeps, businesses, small to big shops accepting bitcoin as mode of payment. Going further online shopping sites with easy to make payment. I’m not saying those systems which acts as middle party so that we can easily make crypto to fiat payments.

It should be direct.

But all of this not happening as of now. Even though we have some countries accepting bitcoin but there are more countries than that who do not like the idea of bitcoin.

Moreover defining its value isn’t fixed. Would be difficult to streamline product and services prices to unless you don’t agree to state the price conversion 1BTC=1BTC