Shortening a story is much harder than lengthening it. Squeezing out the superfluous words gets you somewhere, but getting out one word per sentence for a page can be erased by the realization you need to add one (count 'em, one) additional sentence.
And to make a story you need to make it more complex -- add a character, make a minor character a major one with his own subplot, turn something helpful into something at least initially hostile -- and weave it in so it's an integral part of the tale. But unless something went really wrong, there's nothing to pull that's not integral to the tale already. At least, for me. Outlining helps in that respect. Even subplots that sprout I generally hook in entirely by the end of the first draft.
So what does one do with a story that's theoretically publishable at its current length, but there are few, few, few markets for it?
Then, there's genre considerations. Some genres have more outlets in the long form. (You never forget getting a personalized bounce assuring you that it's a good story just not right for this market, and then seeing in that very market an editorial observation that they would publish more of that genre if they got more -- even the knowledge that it may not have been the genre that put the editor off, or something else wrong.)
But then, it would need a lot of lengthening to sell as a long work. sigh