Bitcoin has value because it was made for the people due to the decentralized nature. The principle of supply and demand works perfectly fine on Bitcoin. Just like any product on the market, limited supply with increase demand creates value for the product. Bitcoin has a total supply of 21 million yet the demand increases each time as evidenced on the coinmarketcap.
Price fluctuations in the Bitcoin spot rate on the Bitcoin exchanges is driven by many factors.
Heres are some lists:
Rate of adoption is hampered by bad press
Bitcoin's perceived value fluctuates
Too much variance in perceptions of Bitcoin's store of value and method of value
Little option value to large holders of the currency
News about security breaches make investors react
Bitcoin’s high profile losses at are another driver of volatility
Bitcoin and foreign direct investment in countries with high inflation
Tax treatment of Bitcoin also affects the volatility