Structure is essential.
Without it the foot is not reinforced. Plus, pressure from the foot will eventually bend and crease the leather.
The following information is based on my bespoke shoe training. Other shoemakers or brands can vary these steps and materials. But the foundation is there.
Shoemakers provide structure in a few ways. Most dress shoes have some type of heel stiffener (be it leather or synthetic plastic). It strengthens the back-side of your shoe, so that 1) the heel cups your foot and 2) your inserting foot doesn’t crush the delicate upper.
Dry, tanned thick leather is quite inflexible.
Here is an after photo of a leather heel stiffener that has already been cut and skived from the veg tanned leather to fit the shoe.
The shoemaker then dampens the stiffener with a cloth then nails it to the last. It may take hours (or a day) to dry. The leather is best all dry.
The purpose of nailing (and hammering the stiffener) is to conform the dampened stiffener to the last. Some shoemakers skip this step because it‘s more time consuming, but I believe it adds to the shoe’s quality.
Once dry, the shoemaker applies glue to the stiffener.
The stiffener is inserted between the upper (the leather component of the shoe) and the lining.
The sandwich is this:
Leather upper (outside)
The cap toe also has its own stiffener. It’s cut round to resemble the cap toe. The same process of wetting, gluing, and inserting is repeated as with the heel stiffener.
After fitting the stiffeners, the shoemaker quickly begins lasting the shoes. You want the stiffeners to conform to the lasts the best they can.
Once dry, the stiffeners are rock hard.
It’s very difficult (and not advisable) to reposition or remove glued stiffeners. You can see why they’re so effective at wrapping and supporting your foot.
For more structural information on flat feet and built-in insoles, see the flat feet post.