I love being barefoot, but I don't go barefoot in public because of sharps! I don't typically encounter broken glass or used needles, but both of those things will cut right through your "thicker and tough" skin before you can feel it.

Broken glass is far more common in modern times than it was on the savanna, so it's wise to dress accordingly. You don't have to wear Dr Martens, but a millimeter or two of Vibram can dramatically improve your quality of life.