What about the smart contract use case? Unlike using crypto as currencies, smart contracts offer more than just decentralization as its main benefit; they can actually result in more efficiency (instead of less) as they remove all the middlemen required in processing contracts by executing contracts on a blockchain.

What if the "mass adoption" you're talking about doesn't come in the form of people using crypto as currency on an everyday basis, but rather via companies resolving all contractual obligations (legal & financial) through trustless distributed ledgers?