Who said anything about banks? Gold, silver, oil, food, land, businesses, or whatever. It's simple: Bitcoin has a substantial chance of going to $0. You can very easily arrange other assets so that they do not have a substantial chance of falling very much at all. Even dollars in a wobbly bank + BTC, which is just about the worst possible diversification strategy, is nevertheless much safer than only BTC.
Diversification doesn't make you money, but it does help lock in your newfound wealth. This shouldn't be controversial as it's merely basic statistics that if you have $10 million and spread the risk around it reduces the chance you will ever not be a millionaire anymore. To me the value of being a multi-millionaire is not that much less than being a multi-billionaire. YMMV.
Ok ok. I will cash some out at $1000.00 and buy myself a brand new Ford Raptor pickup, a couple more AR-15s, a shit load more ammo and that AR-50 I have been looking at for awhile. Yes I am a redneck that was raised on a farm & ranch in the middle of no where. lol