In my opinion, the risk in investing bitcoin is so small. Because you bitcoin price is increasing even is unstable. Yes sometimes bitcoin price decreases, but most of the time bitcoin price increase. Over a month it increase to 20-30%. If that case a long term of investment you will earn plenty of money.
I think what you are saying is true because bitcoin is not a stable currency so a lot is goin gon every day it goes up and down in value so that is why i should't risk it to put all of your money on bitcoin but just a small amount.