Because when you save bitcoin it is
like an investment that you can use
when you need it.
Yeah, even though Bitcoin is a great investment, you should not put all your money in it because we all know that Bitcoin is very volatile and weak. Its price can be easily manipulated by the Whales and if they want to dump that in an instant, they can. Also, I believe in the saying that "Don't put all your eggs in one basket". Try to find another investment that would surely give you a decent amount of profit. In this case, you can minimize the effect of loss in case Bitcoin is destroyed (which is impossible to happen).