Because sometimes that isnt necessary. Sometimes less is more. When writing,especially fiction, you do so to tell a story. Sometimes that story spans chapters, sometimes only a few hundred words. Quaninrty isn't as important as the quality. Some ideas become streched too thin when made into longer stories, while others require the longer length. So the reason why varies. Perhaps a writer doesn't wish to have to come up with more details or plot. Or perhaps the writer has told the story in its entirety, with nothing left to tell

I do it because don't usually have a high attention span when it's just words, which is why description and dialogue are important writing parts to me.
I actually hear it's good for most writers to do flash fiction. You're writing almost every day, just a little project, and it helps with writing bigger stuff, because flash fiction can help people learn on cutting away unnecessary parts and sticking to the important stuff.

I enjoy writing short stories because you get to flesh out an idea that's been bothering you all week long. The idea whispers in your ear, the idea haunts you while you sleep, and the idea drives you insane! But once you put it down on paper and give it a little story, it stops bothering you.

Ok, that was my troll answer. My real answer: you finish a story pretty quickly, there isn't as much stress, and usually some one can read it in one sitting.

A story is only as long as it needs to be. I love all lengths, from the dribble to the drabble, the short story to the novelette, the novella to the novel. Every story is different.

I write short stories because its easier for me to focus on. I can tell the story without having to worry if I have to much boring/filler parts, while still saying everything that needs to be said.

I'm actually debating on whether to turn Imperfect, one of my short stories, into a longer work.
The same could be said for Mind Control too.

Short stories are just that; short. You don't always need 50,000 words to get an idea across. Sometimes you can say the same thing in only a few pages.

I write short stories from time to time simply because I enjoy it. I tend to lean towards horror when it comes to shorts but like most have said, sometimes less is more. you don't need a whole book to get your idea out.

Sometimes, everyone needs something to rely on for relief from stress in the real world, or maybe just a break from school or work. Sometimes, planning on writing long novels just piles onto the work and anxiety people can have. For me at least, I can pour out every single idea for one topic, and of course, it won't always last for multiple chapters. They give me a sense of relief I guess, and it can also become a longer piece work as well. It all depends on each person ^^

I write short stories because sometimes people are in the mood to read, but dont have time to read a twenty chapter book. Like others have said sometimes less is more. I have a book that I update of just short stories I write called A Cup of Tea to Read. Id love for you and others to check it out and tell me what you think! :)