Well, I didn't know the origin, that's interesting. I'm still very skeptical of the rule.

There are other fire safety rules in the US that are considered sacred, like residential buildings more than three floors having multiple staircases, but these building codes don't exist in Japan or Europe and fire deaths per capita are just about the same. Meanwhile, it significantly increases the cost of building housing in the US.

I imagine there are lots of places without this socket rule, and if some economist would look at the rates of electrical fires between these places, that would be amazing.

I just hate this pattern of regulation in general. Step 1: identify problem (some building materials can cause cancer). Step 2: Come up with some countermeasure (put a sign on every building saying that the building materials might cause cancer). And then they stop. They forgot step 3! Step 3: Check if your countermeasure actually did anything useful! Did cancer rates go down after prop 65? Yes, but when when you control for smoking rates, no, the effect of prop 65 seems to be nothing.