Different people have different preferences. Just like how some people prefer to use cash when dealing, some prefer debit card, some credit card and etc. Each method have their advantages and disadvantages, but people still use them. Same argument for bitcoins.
Yes its true, every people have their own reason why they still invest and use bitcoin. Some of the people like the security of bitcoin and the profit they get even if they wait for a long time, maybe they want a long term investment.