Because I don't find this particular problem on the NSX. There is some slight bend on the lower fairings, but not in the middle of a body panel. And certainly no squeaking like this:
http://youtu.be/8ID3uTQWLdA
Granted the C7 is a great improvement from the C6 and C5, but it's still there. Just something I was shocked to discover on a C5, and amused to still find on the newest iteration (although it is much improved). And no, it is not a big deal. I never said it was. Also, before you go finding some weak spot on the NSX, I will admit I haven't been over every inch looking for bend. I just haven't noticed any off the bat personally.
You can say whatever you want about about weight savings. They have marketed all of the vette's negatives in the past as advantages (leaf springs, balsa wood construction, etc.) but it's really just about saving money.
I'm not knocking the vette for anything else. It's still arguably the best sports car bargain out there. It's not for me personally, but I give them all the respect they deserve (performance, bargain, history, etc.). However, build quality is not one of them. They are improving, and will get there some day. Just not there yet.
I can't find the documentary, but they showed an inside look at how they glued the roof onto the ZRI: the worker looked completely uninterested in perfection, and just eyeballed the fit/finish and said "close enough." Seriously, on tape. It's quite different from the work/perfection ethic in the NSX factories.
Then when you heard about the roofs flying off of vettes early on in production, it all made sense.
Again, the vette is a great performance car. I am not denigrating anything else about it. Don't take it so personally. Nice vette.