I could probably trade my house for a Lambo as well, doesn't make houses a good currency. The few places that take crypto are mostly doing immediate swaps for USD to avoid the risk of price changes and are very much the exception to the rule.
A currency that doesn't maintain a mostly stable value is useless as currency because you can't hold it and expect to get your value back. Can you imagine trying to run a business using a currency that fluctuates 50% a day? how would you pay employees or suppliers? Ever deal would have to be executed immediately to prevent risk. Crypto might become currency someday, but it can't remain a high yield investment at the same time, it's either a lousy investment or a lousy currency, can't be both.
Appreciating currency (even if guaranteed to go up forever) also works quite poorly because no one will want to spend it, and is an economy killer. The slight inflationary nature of the US dollar is actually very important for keeping our economy going since it encourages spending and lending of money.
Basically, believing the current profit in crytpo is sustainable, and believing it's the future of currency are somewhat mutually exclusive. Money can be made on the current market, but those opportunities need to disappear before it can become a useful currency.