The alternative of everybody adopting the safest plug would be too costly and cause too much disruption.
Yes that's it, if you look at the electrical practices in other countries, even if a standard was mandated you'd still have to enforce that. In some Asian countries, they just run wires everywhere and hook 100s of them over lampposts. I watched a British chap doing electrics in Thailand for example, and they don't even run wires vertically or horizontally to sockets; they are just run behind the wall wherever convenient. And they use 220v which is a bit terrifying.
But, I have a theory (after watching people drive in Rome) that when things are actually dangerous, you expect them to be dangerous so are more careful?