This article is from the Living Barefoot FAQ, by Paul J. Lucas with numerous contributions by others.
Yes, broken glass exists, but it is not "all over the place" even on
city streets. Unless it's a recent breakage, it gets kicked/swept into
cracks, against walls, or right against curbs and isn't strewn about.
For the little glass that does remain, again, just watch where you're
But, for the seasoned barefooter with tough, thick soles, most broken
glass is not a problem even if you step directly on it.