It is a chain reaction that triggers the volatility of Bitcoin.  Usage, price, and demand is interlinked with each other and react to the supply, which then triggers the fluctuation of the market.  The Bitcoin market won't operate if one of these is missing.  So it is natural to see volatility if the market is actively operating since supply and demand never stop balancing each other in every transaction.

As the Bitcoin price increases, the Bitcoin usage will be empowered, thus this utility will increase the demand for Bitcoin.  Then, with the demand, it will react to the supply dictating the price changes in the market, thus causing price fluctuation or volatility.