There's a big market for short stories and poems to be published in literary magazines - you'd be surprised. It's actually probably easier for someone to get a shorter work published than for someone to get like a novel published - but don't quote me on it. I've never actually been published myself; only have talked to people who have been.
I like short stories because I don't have to commit to how long it is, and often I have a REALLY stupid story that is just stuck in my head, and I cna't move on to anything else til i get the mess out of my brain, so I write, regardless of how terrible it is, and then I can move on.
I want to write a novel eventually, I am sort of working on... several...
It depends on my mood. I have an atraction to novels because I can get many 'stories' out of them. But I also love the simplicity that a short story allows while still being an amazing gateway to a different world.