Everything you mentioned and implied here is the case for every fiat currency also. Using Japanese Yen to buy food at a US grocery store is unlikely to be pract

Everything you mentioned and implied here is the case for every fiat currency also. Using Japanese Yen to buy food at a US grocery store is unlikely to be practical. Just as trying to use USD in Japan is impractical. The only substantial difference is that crypto's practical jurisdiction is primarily the internet, with some adoption in the "real-world" (shops/services that choose to accept crypto). This makes crypto incredibly practical for online transactions but only practical for real-world applications where it has been adopted. Most crypto payments can be done for cheap, quickly (seconds to minutes), in a practically trust-less environment (not the case for fiat), and are irrevocable (which is a benefit for many). You can borrow crypto with crypto lenders against just about anything legally enforceable, including your house or car (although willing crypto lenders are becoming scarcer and more expensive with the increasingly inconsistent regulatory behavior of the US Government). A major advantage cryptocurrencies such as Ethereum have, is that they provide practically trust-less contracts between entities, evaluated by code rather than a possibly incompetent or compromised judge as you might get in the real-world. Just FYI, payments in the traditional banking systems are very much not immediate, they just appear that way from your perspective. The perspective usually breaks down if you try to move a large amount of currency around, you will get anything from straight up denials, many month waiting periods, money getting "lost" in processing for months, and large surprise fees. The "immediate" transaction illusion you see are just agreements between major financial entities to make transactions appear fast but are limited volume to reduce banks risk. For example, common credit card transactions, no matter how small, are not actually cleared for over 150 days. Based on my experience European banks are no different although I haven't tried it as often as I have in the US.