If you buy a bitcoin in the price of 9000$, yes it may drop, but we have clearly seen that this is what it does. It goes up and down. If you have 1 million dollars and buy 100BTC (900.000$) then the only thing you have to do is wait. Because someday it will pass that number and you will have profit. Am I wrong?
Once people invest in a thing they become conscious about it and always try to check the price of their investment whenever they get free time. And 1 million dollars is actually a big amount to have in a single investment so if one day you see the Price of your investment go down in a single day by more than 20% then you will surely sell most of it so as to Cut back your looses and this will cause you to lose money, so volatility is the reason that people are afraid of investing in bitcoin.