That being said, Bitcoin won't likely scale to have the world or even hundreds of millions of people use it at the same time. Another thing is that doesn't have a fixed unit value, so why would people use Bitcoin over fiat?
Fiat works perfectly fine for me. No one has ever tried to prevent me from grocery shopping with my money, neither have my coffee payments been blocked. Bitcoin doesn't offer one single advantage in this specific field of use.
Fiat may work fine in the time being, but it's subject to manipulation from the government. In contrast, Bitcoin is an open system where no single entity is in control of its supply, emission rate, or digital structure. It's a form of alternative payment system in relation to Fiat or other precious metals in existence. If by any means, our economy collapses in the same way as 2008, then people will become desperate looking for other means to secure their capital.
Considering that Bitcoin and other cryptocurrencies are highly portable, censorship-resistant, and partially anonymous, they're even better than precious metals. One could easily transact in crypto, by simply having access to an Internet connection. Also, it's much more convenient (and easier) to store crypto in small places where Fiat or precious metals cannot be hidden into. Crypto can be used in harsh conditions in the real world, even if Fiat fails and precious metals (like Gold) are taken away by the government.
Nonetheless, as time goes by, Bitcoin and other cryptocurrencies will scale enough to handle most of the world's transactions. And once the next economic collapse happens, people will be ready to do the switch into something decentralized which is out of government's reach. Just my thoughts