There's nothing trivial about the design of the sole grip. On this model, it has been specifically designed to easily repel soil and pebbles as you walk.
The boot is made from natural rubber to ensure it is totally waterproof. Not a single pair slips through the cracks: every pair of boots produced is tested for watertightness! The boot is filled with air and then immersed in water. If no bubbles appear, it fulfills its purpose and is ready for you to wear.