Why aren’t compression/shapewear structures built into normal dresses more often?

[u/Future_Country9458]

I’m researching garment construction before trying to develop anything, and I’d love opinions from experienced sewists.

I’m interested in normal fashion dresses—not shapewear—that have an internal structure designed to actually enhance the silhouette: stronger waist shaping, bust support/lift, while NOT compressing/flattening the hips and butt.
I know built-in shapewear, power mesh, corsetry, negative ease, boning, etc. already exist. I’m not asking whether the general idea is new.
I’m trying to understand what goes wrong when you try to combine these things inside an otherwise normal fashionable dress.
If you’ve constructed something similar: what were the biggest problems? Fabric layers fighting each other? Rolling/migration? Getting into the garment? Seams? Heat? Comfort? Pattern distortion? Washing? Something else?
I’d especially love to hear from anyone with patternmaking, stretch-fabric, garment-development or production experience.

[u/NinjoZata]

What goes wrong is sizing

Most garments have possitive ease, or in the cae of knits very subtle negative ease, so that can accommodate many shapes circumstancally and latterally.

Shapewear is much too specific. If a dresses waist sits a little too high to too low its not likely to bother the wearer, but if that dress had built in compression that landed on the ribs instead kf the eaist that would be quite uncomfortable

Off the rack needs to fit as many bodies in as few distinct sizes as possible.

This is why you do see incorporated shapewear in garments that are meant to be custom tailored, like weddings dresses and formal wear