Fair enough question. What's missing is character. Perfection seems very lifeless and stale to me.
I would liken it to one of my businesses, which is vintage amusement park machinery restoration. I used to restore them to absolute perfection, just as they were when they rolled out of the factory 90 years ago.
But I found them to be cold and lifeless. I started restoring them with moderate imperfections, with essentially evidence of the "life" they've lived over the years, and they took on an entirely different vibe. They were more vibrant, alive, and just plain interesting.
Similarly I find so called "perfection" in women to be cold and lifeless. Also my formula that I occasionally post her comes into play: "Physical beauty is inversely proportional to quality of character" and I'm sure that has something to do with my preference, too.
I'm saying of course that I like minor imperfection and asymmetries, not major ones.
Having said that, I was once at a nude beach with hundreds of breasts flying around. This one girl walked past me with absolutely perfect, perky breasts, the best ones I've ever seen. I have no idea why these two stood out among all the other hundreds within my line of site, but they were stunning, and I'm not the type of guy who typically says things like that. They seemed absolutely perfectly symmetrical and shaped to perfection.
I told her to be careful, she could put my eye out with one of those things, but that's another story... To this day they come to mind every now and then. I find that amazing in terms of human psychology. What were the subtleties of those particular breasts that enraptured me so much? I'll never know...
So while an overall "Barbie doll" perfection does absolutely nothing for me, a perfect body part can set me over the edge.
Needless to say, personal preference in beauty defies all logic. That's part of the mystery of life IMO.
