The argument for is well, maybe with your toes in a steel box, you don't even get the injury. I kinda don't get the whole thing either....
I will say around here steel toe boots would be brutal cold for late Fall early Spring riding.
I also think "steel toe boots" means work boots to most people. Work boots often have laces (bad) and no protection for the type of foot/ankle injuries motorcyclists encounter (also bad). If a MC safety coach says "steel toe boots" are ok, then he/she runs the risk of everyone showing up with lace type, ankle high steel toe work boots and maybe one or two show up with a dedicated steel toe motorcycle boot (they are out there, usually at HD stores).
I have a pair of high quality, over the ankle mid-calf steel toe boots that I wear when operating the chainsaw. I can't imagine wearing those heavy monsters while riding. Absolutely no feel at all and it is like my feet are in cement blocks. They feel like they weigh about 3x what my leather SIDI On Roads weigh.