The whole point of a toddler is that they don't know what it is they're "supposed to do" in any given situation.
So yelling your kid's name with increasing volume, urgency, and anger is not going to make him suddenly realize he should stop walking into the street, dude in front of me.
Yes, except for the part were we have all been there.
I often find myself struggling to get out simple things like,"Stop doing that!" simply because I am dumbfounded by what they just stuck their hand into,covered with peanut butter, or put in their mouth. I am getting a better idea of why we don't expect them to be on their own until they are at least 18 or so.
Good point, I guess I could've added, "...because I've tried this a million times myself, and it never works."