A persons sexual obsession with the shoes another is wearing, not just the foot, but the actual shoes (footwear).
Consider a sexual obsession, that is a psychosexual disorder, it is the arousal of a person due to the footwear being worn by another.
While mainstream society fixes on the sexiness of shoes, it isn't considered pandering to those afflicted with Retifism. This is simply a marketing technique, and most afflicted take an abnormal attraction, arousal, to the footwear worn.
Usually these are more extreme footwear, such as inordinately high heeled boots, or tighter fitting upper wear of a boot, that accentuates the ankle and calf of the wearer.
In the accidental release of data from AOL, it was found that of those who queried for fetish data associated with objects associated to the body, the majority, 64% searched for footwear, shoes, feet. Supposedly indicating a form of foot fetish or shoe fetish.
To become sexually aroused, only when a person is wearing a particular style of footwear. It can be boots or sandals even.
It is a requirement in order for the one to become sexually aroused, to even climax. Hence its reference to being a 'disorder' or 'fixation'.
This can include the collection of footwear, to keep, so that they can relive their sexual attraction. It can also lead to climax, without actually engaging in other sexual activity or touching.
Practice (Associated Acts): The smell or feel of the footwear can also play a part in the overall fetish. It can be the trigger to get one up, aroused, or ready for actions. Usually this is also about the scent of the leather, or rubber, used in the manufacture of the footwear.
The combination of footwear scents, plus foot odor can bring about not just arousal, but climax. Smell is considered a trigger for recalling memorable incidents.
Noteworthy: The 1960's popular British Series, The Avengers featured fetish clothing, most notably the high heeled shoes. Stars of the show also released a 45 single, titled Kinky Boots.
Shoe Fetishism became more widely known during the Late Sixties as well, from the lurid media attention given to the serial killer Jerry Brudos who would kill women, and cut their feet off, to dress them up in his own collection of stylish footwear.
Other shows have used Shoe Fetishism in their episodes, such as Sex in the City, and Family Guy.
Some theorize that shoe fetishism is created during one's infant years, when a new born associates the appearance of shoes, to being lifted up by their parent or caregiver. It associates a good feeling to the shoe/footwear appearance.
Pornography, generally uses such 'props' to enhance the perceived viewing pleasures of members. Mainly the wearing of such apparel is not practical, but is stimulating to a large number of viewers.
This is most noted in straight pornography, or more themed BDSM porn.
Strippers as well as Pole Dancers avail themselves of this type of footwear, to highlight or draw attention to their feet, to accentuate the foot/leg, which stimulates the predominantly male viewing audience.