I can't imagine any 2 pin plug being as mechanically stable as a 3 pin. Certainly here in Asia I am regularly being driven bonkers by 2 pin plugs dropping out of sockets the moment a butterfly shakes its wings on the other side of the planet.
One common complaint I get from my newly arrived expat colleagues is that their PC gives them slight electric shocks when they use it. IANAE (I am not an electrician), but I assume that this is because of some capacitor voodoo in the PC's power supply. The problem is cured by grounding the assembly.
The British plug/socket embodies the British ethos: nanny state, 'cannot be too careful' etc. In British parlance it is 'belt and braces'. But yes I agree it may be overkill.
> I can't imagine any 2 pin plug being as mechanically stable as a 3 pin.
In absolute terms, yes. But in 30 years I have never seen a 2-pins europlug fall from a socket on its own. I still prefer the French plugs with the Earth pin (and I quite like the British one as well), but europlugs are fine and really not comparable to American plugs.
I can see it happening on some very old and very used ungrounded sockets. But with modern recessed sockets yeah not going to be issue. Which actually is an other great design of those plugs.