As time goes by I realize that one famous Psychologist wrote about feet and shoes,  Freud!  

Sigmund Freud viewed perversion like he did just about everything— as likely stemming from periods of disorder in childhood development..  Sigmund Freud claimed that people sexualize feet because they resemble penises.  Another  is that hormones and emotions drive people to imprint their arousal on to certain objects. These hormones and emotions allow them to respond to certain stimuli sexually.

So if the fit appears to look like a penis then women’s shoes and boots when viewed closely look like a vagina.  I have thought this for years.  I look at a set woman’s used sexy shoe or fashion boot and as I view the depths it translates into a vagina that in my view needs penetrating.  The combined odors of her feet and the leather come so very close to the odors of sex.