Boots are the foundation of your outdoor's and work gear, as such you subject them to more abuse than any other item in your arsenal.

You literally beat them against the ground into water, salt, dirt, grease, and grime thousands upon thousands of times.

When leather gets wet, it loses its natural oils drys out then loses it's flexibility. The leathers fiberous membrane will lose its integrity then start to crack and eventually break down.  Once this happens it is lost and needs to be replaced.

Vagrant boot wax prevents this breakdown.