Bitcoin isn't an investment, it's a currency.
It is both, if gold was able to be used in stores (and ultra divisible) it would be a currency and still an investment. You invest in bitcoin over Fiat because it's deflatory while fiats are the other and it's rarity will go up as the amount in circulation spreads to more and more people.
Hmmmm, interesting.....so if currencies are investments then the exchange rate is dropping because people are investing their bitcoins in dollars.