As with any kind of 'safety' accessory, you need to be quite clear what you wish to achieve and at what potential cost.
The purpose of steel toecaps is to protect toes against crushing, such as dropping heavy objects on them.
The most likeley cause of injury in a road accident is impact. Impact energy has to go somewhere. Anything which protects one part of the body from impact has to pass the energy down to the next part of the body.
Some years back, the TRL in the UK tried to tell us we should all have leg protectors on our bikes, because their tests showed a reduction in lower leg injuries when they were fitted. What they didn't tell us was that the reduction in lower leg injuries wes accompanied by an increase in upper leg, pelvis and spinal injuries. I'll take my chances with the lower leg injuries, ta!
So, the steel toecaps may protect your toes, but will increase the chance of breaking your ankle.
If your reason for wearing steel toecaps on the bike is simply that you're riding to work, then don't let me put you off.
Incidentally, the type with the external toecap is more likely to damage your bike when throwing your leg over.
Do as you will, but harm none.