Why walking in VR? …cause… like… walking !!
Why running in VR? …cause… like… running!!
Why would you go all the way to the moon, to just look around from a sitting or standing position, or (worse still) point and click to get anywhere?!
That may be ok for some, but for many of us the normal action of just being able to walk through an enchanted maze, walk up to a Cherry Blossom tree in bloom during Spring, and to run after a Leprechaun is part of what you would expect in a fully immersive Virtual Reality experience.
Walking and Running is just a part of the realism of the overall experience.