Simply because the WHALES take the profits whenever there's a 5 to 10 percent growth. The bottom line is Swing trading and Day trading is real and the HODL method is just what it is...
Even if the whales exist everytime no one can actually control the value of bitcoin no other than the people who are buying bitcoin and all of the users has a control to the value. What i mean is all people using bitcoin has a power to control bitcoin if they cooperate to buy more for sure the value of bitcoin will increase again to $20,000.