Because it is at the reduced rate like this that you can buy and make profit by selling when it rises. Or do you prefer to buy when it reaches it's al time high where you probably can't purchase it. This is the perfect time to invest into bitcoin and wait for its bull run hopefully ending of this year.
This is one of the opportunities to have bitcoin at a low price because of its downward position. It is speculation, but the bitcoin curve is like a reflection, after going down it definitely goes up.
Invest while there are still opportunities for low prices, this has been proven by many people around the world who enjoy the wealth of bitcoin.