A long time ago I was told that when designing, "Form follows function". This was coined by Louis Sullivan in 1896. What he actually said was "form ever follows function" and he was talking about architecture. It really doesn't apply in costuming where the clients' choice, the purpose and the status of the garment means that 'function follows form'!
Still, any garment has to be built on firm foundations and the 'architecture' will not be right unless you work from inside out, building the undergarments layer upon layer to give the correct shape.
The stays in the picture are from the last quarter of the 18th Century, made in silk and hand made from start to finish taking over 40 hours.You may well ask why we've made something by hand when it will hardly ever be seen. I suppose there are a few answers to that.
It could be that they end up on display for educational purposes somewhere, where the stitching and construction can be seen in great detail.
You know, I was once in a design studio, when one of the creative people shouted "It will do!" about one of the jobs they were working on. I walked out. If you're not giving of your best, you're not doing your job.
Gini once said that "good design costs no more than bad design".
What I'm really saying is the stays are for when "That will do!" - just won't cut it.