I am so far above that average I can't imagine only having 170 items to wear. I have over 100 in just shoes.
I do have a need for a 4 season wardrobe so that accounts for part of the above average excess. \
Also because of digestive health and other issues can my weight/size can change in an instant so I have the size I usually wear and I keep a wardrobe of a size one smaller than I wear knowing there will be a time when they fit and what I currently wear would be too large in most items. There were times when I lost weight quickly and didn't have smaller clothes saved so I would get tired of wear too big items and buy smaller ones, then my weight would come back and I needed my normal size. So I have learned to keep both sizes.
I love clothes and would not be happy wearing the same items over and over. I enjoy putting various items together in different ways (in other words I like to play clothes),
I know I buy too many clothes but I am a purger as I like to organize and I do donate a lot to keep my closets/dressers/amoire in good shape and I am fortunate enough to have plenty of the above closets, etc. I keep the too small stuff in storage bins til they are needed. I do go thru them when I purge also.
Maybe since the survery includes women from all over the world, it included countries where seasonal clothes are not needed along with other issues such as the French women stated abovt who have small amounts of clothes and that would bring the average down.