Seriously though, what is the point of it anyway?
People who are mining are mining it for money, real money.
People who are trading are doing it for money, real money. Large or small quanities, they are hoping the market will rise so they can cash in. Note, CASH in. Something that bitcoin isn't.
It is just a way for people to make money. It is the real reason. You can say people in black market uses it, well when the value hits the floor then they will go back to the dollar. Honestly, how exactly would you do trade with a currency that fluctuate by 50% in a single day? If you agree on a price and finds it is now worth twice as much would you sell or would you wait? On the other side, how would you feel if you all of the sudden need twice as much bitcoin as yesterday?!
And it always come back to this, the whole thing is measured against the dollar. For people like you and me, the only way this bitcoin is of any use is to cash out and get some real money from it. If I can't buy my lunch with it, it is worthless to me.
No international transaction fees, anonymity (to a degree) and quick(ish - certainly quicker than some banks are) confirmation of transactions are some of the reasons people are using BTC. It's not just for the cashing in, but in the current market (and lack of adoption) yes, you'll need to exchange for many things. Much like going to Europe with pockets full of Sterling is pretty much pointless.