It's not the getting dirty part I mind, it's the memory of getting stepped on several times and losing toenails.
It's also the memory of the time I stepped on a pitchfork I had just gotten done cleaning stalls with in soft-soled rubber boots, getting a tine through the foot, and having to get a tetanus shot and soaking in epsom salts.
If you're more graceful than I apparently was as a child, by all means, go around barefoot. As for me, I wear hard-soled boots.