Why? Because people’s health has a decisive impact on the outcome of their work.
This quote from Epidemics and Society solidified it for me.
In its turn, disease frequently had a decisive impact on the course of military campaigns and therefore on international politics and the fate of political regimes.
A decisive impact, beyond technical skills and tactics.
In 370 BC (!), Xenophon wrote in Cyropaedia
And pray what will be the use of tactics to an army without supplies, without health, without discipline, without knowledge of those arts and inventions that are of use in war?
We are backwards in terms of how we think about health and fitness.
Sure, we talk like it’s important, but we act like it’s optional. Something to do when you have the privilege to do so.
But it should be a public good, like roads.
The father of Cyrus the Great counseled him,
"My son," Cambyses answered, "these are the principles you must apply to others."
"What!" said Cyrus; "do you think it will be possible for the soldiers to diet and train themselves?"
"Not only possible," said the father, "but essential."