IMO, much of the WIS fixation on movements comes out of a desire to add intellectual substance to an otherwise pretty vacuous and inconsequential hobby. I'm sure that stamp collectors and furries have similar classifications and hierarchies to rationalize their pursuits. That said, there are many ways that an optimized movement can substantively improve a watch, in such areas as accuracy, reliability, dial configuration, case proportions, and useful complications.
I'm sure you know the original purpose of finely finishing/decorating a movement was to remove all rough surfaces and edges so as to reduce friction that could rob a movement of accuracy and power.
Today, with the machines that are currently available, most movements are quite accurate, and the finishing/decorating is IMHO about creating something of beauty and something thats not a disposeable good, such as a plastic quartz watch. This is true with many high end goods. Why do people buy a Kiton suit or a John Lobb shoes, or bespoke suit and shoes? There are suits and shoes that cost less that have nice fabrics or good quality leather and varying degrees of hand workmanship. Yes, someone might seek out a bespoke suit if they have an unusual build or issue that makes something off the rack a tough fit. But for a person of average build, a $1,200 suit and $400 shoes may last a person just as long as a $5,500 suit and $4,500 pair of shoes. So why spend the extra money? I've never seen anyone undo the buttons and roll up the sleeves on a suit jacket, when the jacket sleeves have real button holes. Except prior to making a purchase in a store you don't generally see people other than tailors or cobblers spend a lot of time looking at the stitching inside a jacket or inside a shoe. Anyone can buy a mass produced, machine made suits, shoes, watches etc. On some level hand workmanship on a watch, or finely finished item of clothing represents real effort, care and quality in a good. Its something to take care of, to enjoy, to admire for its history, its beauty and on some level its rarity. If none of these factors matter than why not wear a cheap plastic watch from the covenience store?
While some people don't care what movement is in a watch, there is no denying there is a vast difference between the movement found in a Tag, Omega, Breitling, or Rolex and say the movement found in a Lange. Granted the others are designed to be more rugged, and the Lange is a dress watch that can double as artwork for the wrist. I think there is more to the issue of interest in movements than simply being an act of inserting intelectual substance into a hobby, but to each his own.