1. It's an alternative investment. 2. You can make almost anonymous payments. 3. It's a place to store and hide value.
1 is for the gamblers, 2 is for the people who like to get high and 3 is for anyone currently going through a divorce.
To the moon.
2. Cypto currencies could be used as a reserve currency http://btc-times.com/cryptocurrencies-will-become-reserve-cu...
3. could be used as a settlement system
all major currencies fluctuate, too. the reason you dont see it is because all other prices are quoted in terms of those currencies.
when the price of gold goes up, for example, it may not be gold going up. its possible that the currency is just losing value.
you've just accepted that the price of USD is what you agree on. in a "bitcoin is the currency" world, bitcoins value does not fluctuate at all. everything else does.
And yes, the price is obviously a popping bubble. That's painfully clear.