What do you think is the real reason Crypto is not becoming Mainstream?
Usability. The internet was around for a long time but "normal" people didnt use it until everything became a picture button. People are still afraid to lose or get hacked for their money with no way to recoup it. So once usability becomes a lot more user friendly and security becomes a lot more tight. That's when the sharp curve up will start.
Bitcoin usability is the main reason for bitcoin to become a mainstream digital currency, in fact, many companies and countries such as France, China and Facebook creating their own digital currency.
The main reason probably because bitcoin volatility, the price can spike up and tumbled within hours, who wants to invest $10K today but tomorrow the value of bitcoin loss $3K?
Another reason is Government regulation, it's a good thing if a country acknowledges bitcoin as an asset like gold or bonds which everyone is free to trade it, without tax is even better. If a country declares bitcoin is free to use by the citizens anytime anywhere, then it's going to be mainstream.