I totally agree, and there are exceptions to every rule. Gyms, work, climbing walls, etc.
As far as the city part... I've walked around barefoot in LA, Paris, and Madrid. And although you do have to be a bit more cautious (and wash your feet as soon as you get home).
Glass is a fallacy, there isn't that much broken glass out there, and once you've worked your feet enough that the soles thicken (thick and alive, not hard white and dead) glass is no longer a problem.
Everything else is an ick factor, and I watch out for landmines left by dogs (and sometimes humans) YUCK!
Once you learn that you create your own reality and that you are fully responsible for your life, you can begin to see the world as it is and then you realize the limitless possibilities.