Why do you wear tennis shoes or crocs on Yom Kippur? I know you are not supposed to wear leather shoes, but many non-leather shoes are just as comfortable, so what is gained by wearing them?
A leather shoe is what our life is all about. Except on Yom Kippur.
A leather shoe is an animal hide that has been processed and refined. A coarse piece of rawhide is stretched and boiled, treated and purified, to make a final product that is smooth to touch and comfortable to wear.
This is our soul's mission on earth - to take the crudeness of our inborn personality and refine it, to take the rawness of the world and tame it, to harness our natural animalistic instincts and transform them into refined character traits.
So leather shoes are a symbol. They represent the work we humans are supposed to achieve in this world. We do this work every day of the year, except one.
One day a year we withdraw from the physical world and retreat into a world of pure soul. That day is Yom Kippur.
On Yom Kippur we resemble angels. We do not eat or drink, and we do no physical work. We escape for a day to a spiritual haven. And we don't wear leather shoes. We are not taming any animals today.
By the end of Yom Kippur, your body may be tired, but your soul will be refreshed. You will be ready to put your leather shoes back on, and begin again your task of taming the animal. Because no one else can fill your shoes.