Discipline and Drill
Drill is a coordinated dance movement that requires discipline.
It does help exercise the muscle of willpower, and thus makes people more willing to apply that willpower/discipline into other places of their career.
However, the cost of time invested into drill, which no longer produces a useful skill... i.e. battle formations... is obviously not worth the investment when that time could be used to build a habit that could not only 1) build discipline, but 2) be replicated on the battlefield.