footprints

These traces are impressions or images left behind by a person walking.
They may either be indentations in the ground or something placed onto the surface that was stuck to the bottom of the foot.
How come footprints are only visible on soft surfaces, such as snow, sand, mud and very brief in water and faint when walking on leaves?
Traces on these surfaces are not forever, not lasting we are not leaving them for anyone else to see.

Apparently the Foot tends to be approximately 15% of the person's height. I am 164cm tall, which means my foot should be 24.6 cm, my foot is 23.9 cm.