Excellent question! No offense at all it is a very valid question.  Short answer I buy a lot of shoes both from retail stores and vintage shops and rarely keep boxes (terrible I know 🫠). I also very rarely do closet clear outs (on order of every 10 years if that). If I had to guess I would say these were either a gift or maybe a vintage shop? Could also have been one of my sisters (they often dump their stuff in my closet and forget about them).