Volatility is the main challenge for mass adoption of crypto for payment
Bitcoin and many of the early altcoins were created with a view toward providing individuals and entities with a reliable store of value and payment mechanism that is not reliant on fiat currencies. The underlying motive was that value storage and payment should be carried out via a network collectively owned and controlled by all the participants, rather than by a centralized authority like a nation’s central bank or a global tech corporation.
In practice, Bitcoin and other cryptocurrencies have proven too volatile to serve as a primary store of value for many; though up until now they did have value as investment assets that gave strong returns which were relatively uncorrelated to mainstream economic indicators. Cryptocurrencies, so far, have also proven both too volatile and too expensive to replace fiat currency for most practical financial transactions.
Stablecoins emerged as a partial solution to these problems, reining in volatility by pegging their values to fiat currencies. However, this renders their value directly susceptible to manipulation by central banks and associated corporate interests, somewhat obviating the point of having independent digital assets in the first place. Governance of the major stablecoins has also been highly centralized in nature, leading even further away from the initial democratic ethos of the crypto space.