I think Char GG very likely has the right answer, that there are as many reactions or opinions as there are women who would answer the question.
However, after reading so many posts by CD'ers that discuss their wive's reaction and a few from GG's that shared their thoughts, I arrived at the following generazation. I admit up front that what follows is a gross generality. Here goes.
Many GG's believe that wearing their wedding gown on their wedding day, including all the other special preparations (hair, make up, selection of accessories and lingerie, etc), was the day that they felt the most feminine and felt the most beautiful. For many GG's, it is a day when they feel the most special, most attractive, and many even imagine themself as a "princess."
Secondly, I believe that many GG's also do not take kindly to their man intruding on the memory of that special day, even when that GG is supportive and accepting of their man's need to cross dress. I believe that many women draw a red line when their attitude is, "don't tread on the memory of one of the most important days in my life, when I felt the most feminine and most beautiful."
Lastly, many GG's have a spiritual reason for keeping their wedding day as a special day. I will not discuss that any further because of the very wise rule to not discuss religion on this blog site.
I welcome your thoughts on my highly generalized conclusions. Does my analysis have any merit? Even if it doesn't it's sure fun to talk about.