The game mechanic doesn't recognize moist soil or wet, hence why it removes the realism from the game
This suggestion was made to ensure it would put more realism into the game, here's what I came up with.
After raining the soil will:
Hinder the player and the zombie's walking speed due to muddy area
Reduce the speed of a automobile on a dirt soil that has been rained on for longer period of time
Be possible to trip over if the area has experienced intense rain and the player was running
Moisten up the furrow dug by the player given the fact that seeds don't need water, soil does
Project zomboid focuses on realism so I made sure to point this out in case it was forgotten or not thought about.