Personally I find it essential to learn the craft from the ground up, rather than beginning at the top and pick up bits and bobs from below. Writing a novel is as much about writing stamina and perseverance as it is actual craft and skill. There is a flawed logic floating among writers that people read novels, not short stories, so why should they bother with anything else?
The simple answer is for the love of the craft. All those skills one pick up from learning the little things are applicable when your move up the ladder. Learn to crawl before you run. That's not to say you shouldn't write a novel, but the easiest way of falling into the "writer's block" trap and quit altogether is when there's not enough groundwork done.
It's also a wonderful feeling to have finished a short story, regardless if it's a 1000 or 10,000 words. Remember what Stephen King said: "The first million words are just practice", so you might as well practise on something you can finish.