Shoes are like clothes. I find that even though I have a lot of them, I end up wearing only a few of them. I have definite favorites each season. It's hard for me to know in advance which are going to be the favorite and why? Last summer I had a pair of platform wedge Naot sandals that I wore Several times a week. I have a lot of shoes, so repeating the same pair multiple times in a week is significant. The year before, in the summer it was a pair of Cordani sandals. This winter I wore my Bos Co. Hiking boots the most, with my charcoal Aquatalia and charcoal Arche booties coming in together in second place for most repeat wears.
I suspect it has to do with comfort and outfit coordination. I also wear orthotics with closed toe shoes, but not sandals. I purge by signs of wear, fit, and if a shoe still fits well with my style/items in my wardrobe. I have a few special shoes that coordinate with only one dress. If I could find a shoe that served multiple purposes that could substitute, I might toss those.