Because of panic people lose a lot of money. When market falls many people sell their assets. But to earn money on cryptocurrency it is necessary to sell assets not during the fall of the market but during the rise of the market.
Usually people panic when fall of the market starts and people do not know how long this fall of the market will continue.
But after the fall will be a rise. It is necessary just to wait till the rise.
But not all the people are ready to wait.