Osha allows steel where plastic (fiber is a plastic) has issues. However they have complex rules and none of the industries I work with will allow steel.

I've been wearing them all my life all over North America. Very few industries require metal-free footwear. Composite toes (since we're getting carried away with various terms, that's the actual term and fabrication method, which is fiber mesh and epoxy) still have downsides. Those don't apply if you're a white collar guy and just need them because of regulations.

But if you're an actual worker that relies on them to save your toes, CT has much worse puncture resistance than ST. So it's trivial to puncture with a framing nail gun or cut through it if you rest a board on your toe, for example.

They also shatter when something heavy falls on them. If the thing bounces and you're quick enough to pull your foot, then great. If not, the second bounce will be shattering your toes and your boot will be filled with fleshy composite soup that is impossible to save. A steel toe in that situation will just bend and odds are good that your foot will be salvageable.