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.
Moreover to this statement, Bitcoin is just like an oxygen that it is priceless to breath but it is very important for our lives and the relation to this is investing to Bitcoin can acquire for an average price and when you keep it for a longer time, the value of this are incredible that we need to survive our investments