Bitcoin is more like a speculative stock than a real currency. While a few people use it to conduct transactions for goods and services, the majority buy it for speculative price appreciation. That causes wild swings up and down.
Exactly. Bitcoin is thought of as a currency but really isn't. Plus there are tons of people speculating on it, which drives the price up and down drastically because it doesn't take that much money to do so. More than I have of course, but 10 bln is not a lot for rich players.
Even real currencies have volatility against each other. Usually not like bitcoin though.