This would in effect straighten posture and extend the upper body of the wearer to her fullest height (and restrict movement or slumping so that this posture would be maintained). Such emphasis of height and restrictive movement would coincide with Tara's lecture points that grace, above all, was treasured. The pleating of the stay's bottom would allow for better bending at the waist and, if the stay were "tight-laced", would allow for any "displaced" body fat to move down. This doesn't seem to matter as the skirt styles were so wide that they would have hidden or masked any disproportionate hip size.
The corset worn later seemed to have lost the posture-straightening pupose of the stay and appears to have be specifically a sculpting device. Where the stay would have pushed the breasts up but flattened them, the corset would lift the breasts up and sculpted them. In fact, everything about the corset's design would sculpt the female form. The breasts would be accentuated; the curve of the waist would be drawn in; the corset continued further than its predecessor by extending over the hips and "tummy" area. Now displaced body mass (internal organs would be included, not just superficial weight) would be pressed downward more internally and, along with the pelvic bowl, add to a more desired effect of sculpted,curvaceous hips and buttocks.
Whereas the stay seems more functionary, the corset seems more aesthetic. The stay draws attention to the grace of(or lack thereof) the wearer; the corset draws attention to the shape of the wearer, if at the detriment of movement. This change in focus changes the focus of sexuality from movement to form. One look at a website like www.deliciouscorsets.com shows this intent with catalog categories named "DeSade" (sadism) and "Masoch" (masochism). In fact, all the corsets are given names of famous literary figures associated with sex/sensuality. Hey, you might not be able to move as well in a corset, but you'll look damn good not doing it.
As far as would I wear one...it's never really crossed my mind. But then I'm a guy who tends to wear baggy clothing to hide the fact that I'm overweight and not a desired shape. A corset would not do anything to my frame that I would rather focus on, like better built arms and chest. As a man, my goal should be to be in a position that I can take my shirt of and not feel inadequate. Besides I have the grace of a monkey and this would be highlighted in such a restrictive garment. At least to the people that know me.