Your footwear should have an impact on your movement speed and maybe other give other effects.
For example, walking barefoot on concrete still gives normal speed, but on dirt and similar surfaces, the speed is reduced to eg. 80%, and even more for mud and more extreme terrain.
There could be other debuffs for walking barefoot on extreme terrain except speed, for example losing stamina faster if you run trough extreme terrain barefoot. Or standing on hot concrete for too long barefoot makes you lose stamina. There are many more possibilites.
Basic shoes or sneakers would provide immunity and give full speed on dirt terrain and similar, but would still lack in more extreme terrains such as mud.
Boots would give full speed and immunity to all terrain. They would be more uncommon and have increased spawns in military locations, but not exclusive.
Another potential idea is that all footwear slowly deteriorates and needs to be taken care of, or another possibility is that footwear like shoes give 100% speed and immunity on all surfaces, but deteriorate when used on extreme ones.
What do think?