It has the force of law in the US.
And...??
Show up at Walmart with dollars and you can buy stuff. Show up with bitcoin credits
or gold bars and they will politely decline to take them.
Unless you preferred larger bills than $100, which are now illegal.
While there are a growing number of places that accept cryptocurrencies online,
most people do not use them for that purpose.
And you must accept what happens to the purchasing power of every dollar you hold,
thanks to policies of the Federal Reserve.
There is no free lunch. Just choices.