Lack of any centralization (Central Bank) makes bitcoin Heavily affected by the change in supply and demand law.
if more people decide to use bitcoin (More Demand) with the limited number of bitcoin "Scarcity"(less than 21 Million), the price will rise sharply.
The main factor determining the currency value is Encourage individuals to buy currency With the possibility of conversion to basic currencies easily.
All of these factors make the value of Bitcoin increasing in the future.