You can save in Bitcoin if it is convenient for you, you can divide your savings, leave some in fiat, buy some Bitcoin, and send some more to buy assets that can generate passive income. No one forbids you to save everything in Bitcoin if it is more convenient for you, but you need to remember that Bitcoin is a highly volatile asset and in years when there is a bear market, important savings can lose a lot of value, if you are ready for this, then of course you can save in Bitcoin and hold your savings. I am inclined to divide my profits into different assets, diversification is a smart move.
Diversification is a great tool for investors, but if we look at the historical chart of bitcoin price, it is clear that few investors are in the negative and their losses are not so great compared to investments in other assets. In addition, national currencies are subject to inflation, so Bitcoin is a great tool for preserving value. Diversification implies additional risks that can lead to losses, so sometimes it is better to just hold Bitcoin than to try to predict market behavior and geopolitical events in the world.