I think the biggest reason why Bitcoin is so volatile is because it is not regulated and the fact that its supply is limited. Since it is not regulated, anyone can buy any amount at anytime they want, same for selling the coins. Having said that, since the supply is limited, it price movement is mainly based on the demand, people's demand and interest for Bitcoin. So essentially, the price is based on the people's actions, it directly affects the activity of the price, hence volatility.