That's one way to do it.
But I'm usually of the opinion that there are ways/times the writer must control the story, not the other way around, particularly if you want to sell the story to one of the big pubs. Word count is one of those things.
A publisher isn't going to want to look at a 140K romance novel. Nor will you sell a 30K romance novel. (Okay, that's not entirely true - there are some markets these days for novellas, but they're usually for very specific types of stories. Particularly the hotter stories.)
Anyone looking to write category romance MUST control the word count, because HQ's requirements are most specific. They're not suggestions.
So, I think keeping an eye on word count can keep you in control, keep you from rambling off too much, keep your story moving forward at a good pace. When you know you have a specific amount of space to tell the story, you write tighter, IMHO. Do I really need that scene, or can I portray that information in another way?
That's why I don't write short contemporaries. <G> At least, not at this point. I haven't mastered that tightly controlled story format. I haven't done too many short stories, either, for the same reason. Now, flash fiction I can do. But gosh, my hat is off to the people who can do short.
Susan G.