I don't get it.
As someone currently living out of a 40L bag [1], I don't feel any great cognitive load or emotional weight lifted. We sold all of our stuff (books, desks, cars, house) in order to do a round the world trip. The process really sucked.
You do save money from living without cable or not buying so much 'stuff', but I find that to be the limit of the benefit. I have no reason to believe that we won't be buying back many of the things we sold prior to travelling. In all honesty, living out of a bag makes me want more. I miss having more than three shirts or two pairs of pants to wear.
Minimalism is fine, but all the proselytizing around it makes no sense to me.