He doesn't see people being willing, en masse, to convert the currency they receive (in a paycheck, for example) into another currency unless absolutely necessary. This is a chicken-egg problem if you want crypto widely adopted, where you need the vendors to adopt crypto but it'll likely have to be the government or company first that distributes it to citizens/employees.
He specifically mentioned Switzerland as a great country to explore a system like this (think Anti-Venezuela lol); if they were to found/back a decentralized currency, it could quickly reach mass adoption and we could actually function in society on crypto. I'm interested to see whether Switzerland could go that far with their approach.
The incentives that could be provided to make it worthy for a country like Switzerland to found/back a currency which they don't ultimately control are unclear, but nonetheless an idealistic concept.