component grounding

So this whole thing about grounding audio gear. There are millions of pieces of vintage audio gear out there without ground plugs. In fact, many don't even have a polarized two prong plug. Yet search as I may, I can't find one situation where someone was killed or seriously injured from an ungrounded piece of audio equipment. I've been in the HiFi business for over 50 years.....Never saw a recall or a warning or anything until recently. This past year I built a Bob Latino ST120 Tube Dynaco clone amplifier. I was surprised to see a lampcord power cord with no ground. When I inquired I was told by many to not ground it as it wasn't necessary and might introduce hum......Can someone show me documented case where injurie resulted from an ungrounded piece of equipment?