I like to use the analogy of the process of building a house because it so nicely illustrates this point.
The builder begins by securing the land and selecting the site for the house. Then stakes are put in the ground where the house will stand. Then the hole is dug for the basement or footings, concrete forms are put in place and the cement truck arrives to pour the foundation. Then on top of the foundation framers construct the floor girders and erect the studs forming the walls and rafters and sheath the whole structure in plywood. Window and door openings are cut in and installed, shingles put on, siding is added to the outside walls, everything gets painted or stained, etc. etc. Then the interior is finished off--wiring, plumbing, drywall, floors, more painting, the landscaping, etc. And finally you're looking at a completed house ready to be lived in.
But what happens if you skip or short change any of the early steps in the construction process? What if the framers, for example, cheated and put the studs and rafters 30 inches apart instead of the necessary 16 inches? Or the concrete mixture was short on concrete and overloaded with sand or the holes for the footings were not dug below the frost line? The house might still look beautiful when first completed (with all those shortcuts and mistakes hidden from view), but it won't stand a chance of surviving the harsh realities of time and weather. And then you're left with something like this:
And my contention is that this happens way too often with scripts when the entire building process is not respected and writers are in way too big a hurry to get that completed "house" up and running.
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I'm the Program Director of the low-residency MFA in Writing for Stage and Screen being offered by the New Hampshire Institute of Art. Our last residency just ended, running from January 6-15, and we are currently accepting applications for starting the program with our June 2017 residency running from June 23-July 2. I'm also a playwright and screenwriter, producing partner in my production company Either/Or Films (The Sensation of Sight and Only Daughter) a professional script consultant, and the author of The Playwright's Process.