A light wind can push grass around to-and-froe but is ineffective against the Oak tree that stands strong and undisturbed. Yet a strong win will uproot the oak tree but is ineffective against the grass that simply moves to-and-froe.
There are times to be the Oak tree and times to be grass. Karate-ka spend a lot of time developing Oak tree principles and are often weak at being soft. These drills (whether you would use them in combat or not) help develop a students ability to flow in stance and technique.