Keeping everything in cryptocurrency is quite dangerous. Assets need to be diversified.
At the same time, cryptocurrency is a very good option, but what if the investment plans fail? This is not so impossible if you look at what happened in the last bull run. There are many investors that has not gained back 20% of the money they lose to various altcoins, not to talk of gaining back the whole 100% this year or next. In many cases, this may not be possible anymore since some altcoins may never hit their ATH again. This is a loss!
So it is not so convenient in the cryptocurrency world as well. But what you never added is the fact that there are other investment opportunities. Instead of we keeping our money in bank and investing everything in cryptocurrencies, why not diversify it? If done properly in at least 5-10 differents sectors, I am sure that nothing adverse can take that way from the person. And this will be a smart move to avoid banks issues and still edge against inflation in a way and try to secure one's future better.