I always thought that was a quirk of photocopier manufacturers. It stuck in my mind because the symbol makes no sense to me.

I didn't realize it was an actual standard. Still doesn't mean the symbol makes any sense, but hey, at least it's a standard.

Photocopiers? Yeah, I saw that symbol on some of them. But then even some of the image results show that manufacturers of photocopiers and printers, particularly targeting general consumer market, let their designers get creative with the shapes, colors and labels on the buttons.

A bit snarky, but yes, I've used a photocopier. I guess the shape of the symbol of the start button on the photocopiers I used slipped my mind.