While wearing your leather or suede shoes, your feet perspire. This, unfortunately, is an unavoidable occurrence. Each part of a shoe that is made of a hide, whether it be leather, suede, calfskin, nubuck, reptile leather etc., will absorb the moisture from your feet.
As you wear your shoes, each step that you take bends certain areas of the shoe to varying degrees. Some materials such as rubber undergo “plastic” deformations, meaning that there is no deterioration of the material. Others, such as leather, will clearly show wear and tear marks in the most-used areas.
These effects adversely affect your shoes when you take them off. Just like a rumpled shirt taken out of the washing machine, your shoes will have a number of creases and deformations.
Apart from proper care, cleaning and hydration, the only way to maintain the shape of your shoes is to use shoe trees as soon as your take them off. Just as you would iron a rumpled shirt, your shoe leather should be stretched as it dries out. This is where the shoe tree comes into play.
Note: We often speak of shoe trees as a means of drying shoes. While shoes or boots must indeed be dry before you put them back on, this is not the main function of a shoe tree. It can speed up the drying process while you are not wearing your shoes, but its primary function consists of maintaining the shape of a shoe as it dries.