You have a point investing all of money in crypto currency is a big risk that you will putting your money in a not sure platform of investment wheather it will gain profit or it will loss but the main reason is if the people who investing in crypto currency have knowledge of how crypto currency works because some people are just investing their money without a knowledge of what totally bitcoin is thats why they lost their money investing to it. So I prefer to all of investors in crypto currency to gain more knowledge about it before putting their money to crypto.
Right before you start to invest in bitcoin make sure you have enough knowledge about in cryptocurrency cause this is your key of success. If you don't have knowledge in cryptocurrency don't try to invest all your money in crypto cause you don't know how to face the risk of investing in it may cause to lose your money.