There's a really simple answer. It's about raising awareness, and promoting the cause of acceptance of bare feet as the non-issue that it should be. Does that sound contrary enough for you? :-P
Seriously, it really is somewhat counter-intuitive. We are fighting to be unseen. I go on about barefooting not because I want to, but because I have to. The eventual goal of barefoot advocacy is to become invisible. We want *everyone* to stop caring about what we wear on our feet. But we're not there yet - barefooters still face discriminatory action, and negative attitudes by others. And until we get to a point where this is not the case, I will continue to be vocal in my support for barefooters and to spotlight the positive benefits of living a barefoot lifestyle.
Is going barefoot really that big of a deal? Of course not, but it can easily be made into one by intolerant people who see it as their role and responsibility to ensure that their ideas of the "norm" are what we all must live by, or by authoritative types who wish to enforce myths about safety and liability or who just gain enjoyment from telling others what to do. Sometimes we are even set upon by good-natured people who believe they are looking out for us. Non-barefooters can't understand until they've tried to enter a business barefoot and been refused entry, or been asked to leave a business for the same reason, or been given strange or even dirty looks by others simply for being who we are.
I choose to share my experiences, and to advocate for barefooters so that when I run into people at work, on the street, on the trail, or inside a store, I have the chance, however small it is, that those people have "read about" us barefooters and will either A.) think of us in a more positive way or B.) not think about us at all.
So to answer the posed question in a single sentence: I am always going on about barefooting so that it becomes an ordinary part of the fabric of our culture, and in so doing, it will diminish the importance people place on what individuals have, or don't have, on their feet.