Why Is the Inside of a Good Shoe Also Leather?

https://inapics.com/are-designer-brand-shoes-like-gucci-worth-the-price/

Here’s the thing: when people shop for leather shoes, their eyes often gravitate to the outside — the smoothness of the full-grain leather, the shine, the color, even the style of the last (that’s the foot-shaped mold the shoe is built around)