Thing is, we all have to look in the full-length mirror and like what we see, or at least not be horrified by it. For some people, that can look like being a living mannequin for something sculptural that could be on a catwalk at Paris fashion week. They want people to see the clothes first. For others, "does this make me look my best self?" is the key question. They want people to see them, not their clothes.
I suspect that a person's figure has a lot to do with it too. Someone who needs to go to Bravissimo for bras and has problems keeping weight off is likely to struggle to pull off an "art piece" dress designed for someone flat-chested and slim, even if it's made in measurements that ought to go around her. It's going to hang wrong, pull across the bust, crease under the arms because of a lack of bust darts and princess seams, and be too big on the waist and hips.
"If you like the embellishment on that boxy evening jacket, wear it" doesn't solve the fact that I can have a size 18 or even 20 to go around my boobs, too wide on the shoulders and the sleeves coming down below my thumbs, or a 14 that fits my shoulders and arms but I cannot fasten up. Likewise empire line anything, the waist seam runs across my nipples and I have to upsize so I look like a parachute. For anyone who isn't slim and small-busted, cut and fit absolutely will affect how we see ourselves in our clothes. It's not restrictive to say this, if anything, it's empowering because I can save so much time when clothes shopping by disregarding anything that I know doesn't have a prayer of working on my body. The Trinny and Susannah books were like someone handed me the cheat codes for buying clothes that I would look in the mirror and say "OK with that" about.