For speculation? To buy on the dark web? To buy online on sites like purse.io? To send money? To do business? To have your money under your control?
What is/are your purposes when yu buy bitcoin?
Some bitcoin users buy bitcoin for investment / business only.but most of bitcoin users buy bitcoin because of speculation. They believe that bitcoin can go further after years ,and they might get big profit when they hold and save bitcoins for a long time. Speculators can dictate the price i guess.