“Is it useful?” is a question that cannot be answered with a simple “yes” or “no.” It depends on who you’re asking. If you’re asking a Venezuelan or a Zimbawean if crypto is useful, you’ll get a resounding “yes.” In the developed world, it’s easy to take for granted sound monetary policy and a stable currency.
It’s not useful enough perhaps to you, but if we set aside our subjective worldview and consider how it could be useful to others, think outside ourselves for a moment, then the argument for cryptocurrencies becomes abundantly clear.
Cryptocurrencies are already useful today (see Venezuela), that it is not more useful globally is because of dollar dominance — something which the world has taken for granted and is not a perpetual given.
Adoption of cryptocurrencies will arise out of necessity, just ask a Venezuelan. It may not be there for you, that doesn’t mean it’s not there.