it is just because of the fear of the unknown.
bitcoin is new, and it is constantly under attack. not a day goes by without media publishing some FUD about bitcoin. specially during down trends which makes them bolder. you don't see the media call stocks of companies that are being traded the most as scam, fraud,... on daily basis but they are doing it to bitcoin.
now add to that the manipulation in the market itself done by whales and any person looking at the market from outside would be filled with fear.
Since the very first day when it was established and presented to world, enemies had flown away. They start making games against this tremendous coin. Bitcoin always revived and so do in future too.