If you have a large number of coins and their total cost is high, then storing them all in one wallet is not a good solution. No matter how good and multicurrency it is.
You are right, I am not sure that anyone can properly protect their security key. as we know it today, there have been so many frauds committed to steal our assets.
if the amount is small and the coins are not too much I think no problem. However, if the amount is in large form. of course we must be more careful.