You know Purple, I can fully understand why anyone would want to purchase their own boots. Sadly, not everyone's feet are created equal and neither are footwear.
A boot that works well for you may be torture to the person beside you.
I have worn "issue footwear" from three different nations, none of them were comfortable, especially on long slogs in rough terrain. The first pair, issued Portuguese army issue footwear, made by Lavoro Calca, were about as bad as it gets, for me anyway. The officers were allowed to purchase custom boots for both field duty and regular duty.
I made a comment to you about Rhodesian issue footwear in a previous thread. I was commenting on "non issue" boots in a pic.
Field duty in the boonies can be extremely hard on both feet and the boots, no matter how well they're taken care of.
My people were extremely proud of their issued boots and kept them brilliantly polished. They only wore them on the base when they weren't on duty or parade. Everywhere else, especially the field, they wore what suited them best, and those shiny issues stayed behind.
Some of my people wore home made sandals, utilizing the tread areas from vehicle tires, with all sorts of different methods of attaching them to their feet.
I wore pigskin leather boots with lots of ankle support and thick soles made from Buna N for soles with a couple of layers of leather between for form fitting and softness. Pigskin is porous and breaths better than the leather from cattle/horses. It doesn't last as long, but that was the least of my worries at the time.