What you are telling is well know by most of them, but their is also some reasons are their are so many altcoin ICO are going so join them their are users who are buying bitcoin from exchange and investing in that ICO apart from that their are also so many gamblers who are gambling with bitcoins so when they are loosing it they buy more to recover their loss. So their are so many reason behind bitcoin price fluctuation, even their are so many day traders who are buying and selling bitcoins daily. So their is no one reason but lot of different reason for the price fluctuations