No good material. The usual material for safety glasses (polycarbonate) scratches easily. A grinder guard would be see-through for about three seconds.

They kind-of do, but you wear it on your face.

FWIW, the reason cited for removing the guards was not vision, but access- it is difficult to get the tool in position when you're working on large objects that can't be re positioned.

Was going to chime in that this is the reason.

I used a grinder almost daily without a guard for years because what i was grinding was 2"+ steel rods buried underground.

I couldn't move myself or reposition the work.

I'm not advocating removing the guards but there are actual reasons why people hate them.

I see some grinders like Milwaukee have guards that can be quickly rotated around the blade. That's not always enough, though. Ive also seen some Welders cut their guards in half, for clearance and at least a shred more safety.