Why must I tweet?

I twit(ter), I don't know why, but I do. I'm quite addicted to it in fact.
I submit I have nothing to sell/market and I certainly don't care for someone who wishes to market/sell me something using twitter or any other means for that matter.
So why the hell do I tweet? ...
Is it ego driven? Must I really share what's on my mind at any particular moment with a network of random strangers?
Then one may ask, why even blog? why even have face2face conversation to share your opinion on anything? it's goddamn loop I say. Sometimes I hibernate from all this junk (twitter, facebook,....) but then I get the urge like a friggin junkie.
Had I kids to take care of, mouths to feed, I may not be so inclined to use these social networks, but how would I know if that's true???

I have a hunch ;) there are a few Pavlov's out there and the rest of us are bunch of loyal four legged friends itching for more....