Well. That's all well and good if you want to write a tight argument and convince someone of the validity of your point on some issue, but that's not how we write books.
I see it this way: argumentative writing is your workout routine. It's healthy, and very good at all around tightening, toning and perfecting you(r writing skills). When it comes to writing literature, however, we get to freestyle. And dance is not always symmetrical - that's the beauty of it. Some lines (or in this case, sentences) will be beautiful, elongated, wordy, they'll fill your soul with all the richness and beauty of expression that is creative writing. But then there are these guys. The short, steady one. In dance, these are the static, heavy movements, and the contrast between the two is what makes a piece so captivating and keeps your reader reading, or your audience watching. Without each other, both sentences become monotonous and dull. No amount of profuse vocabulary (highfalutin-mumbo-jumbo, as Gilbert would have it) will make that sentence new, unless you break it up with something easier to chew on. No amount of defeatist drama in those 4-5 word sentences will grab your reader any faster if you don't incorporate some longer sentences and let your writing flow for once.
See the thing about architecture is it assumes similarity. For every flowery, Grecian pillar, (or sentence) you need three others for the remaining, respective corners of the structure. But with creative writing, we get the freedom to stack a tall, flowering pillar next to a short, squat one, next to a sharp square one and so on. The resulting myriad of sentence-lengths is what creates rhythmic, living writing, with that sort of je ne sais quoi that perhaps now vous sais quoi precisement.
So please, for the sake of all of us reading, vary your sentence length. Nobody. Wants. To. Read. Like. This.