Walking is a wonderful, effective, and easy form of exercise. However, for a martial artist, walking should be much more than burning calories.
If you are a martial artist, by definition your walk should be different. It should be balanced, centered, with good posture, awareness, and extension. Soldiers with or without a uniform have that walk. I study I read showed that criminals are known to pick their next victims by simply observing how they walked. As a martial artist you must not be distracted or unbalanced and never oblivious to your surroundings. The bad guy when looking at your walking style should always think twice about messing with you.
Here is one of the few photos of O'Sensei walking. He is balanced, centered, and well aware of his surroundings, yet he is calm. I wouldn't mess with him. I've read in various articles that O'Sensei was know for yelling at any of his black belts he caught not walking like a Martial Artist.
Walking is awesome, but for a martial artist, walking is a free-form kata that should be practiced consciously daily.