I think there is just a minimal or let us just say a small percentage of bitcoin users do resist of selling their bitcoins in exchange of gaining a large offering of profit in their account. They probably do sell their bitcoins so that they can have some funds to buy more bitcoins compared to the initial earning they have. Maybe in some reasons, people tend to sell their bitcoin because they are desperately in need of money and selling their bitcoin is the only way they can see to gather and gain enough money to sustain their needs. Since people tend to buy and buy and buy bitcoins to maximize their capacity and capability of earning.