Not because I want to support journalism (though I do), but because having a whole newspaper to flip through every day is so much more productive and efficient than getting dribs and drabs through Twitter and free news sites --- many of which are ultimately sourcing through the journalism that organizations like WaPo do anyways.
Realizing in retrospect how trifling the amount of money we're talking about for a subscription is (it's a tiny fraction of my monthly information services bill [cable/Internet, Netflix, &c]), I feel kind of embarrassed for not having done this a long time ago.
I like WaPo but you might prefer something else, like NYT or WSJ. I'm sure all the major papers are solid choices. Most of you are younger than me. Don't be like me! Subscribe to a damn newspaper already.