I think that the reason why Bitcoin price was rising over time because of the continuous rise of the demand which makes it more popular for the engagement of potential investors that boosts up Bitcoin's price added by the fact that Bitcoin was being widely used by many Bitcoin users and consumers who purchases and used them effectively for their own purpose. The law of the demand is always getting into this since in economics where currencies are widely being discussed, as long as there is a rise in the demand in relation with the supply, the possibility for the price increase will be open and constant to keep the balance between the demand as well as the allot supply to be used.