[SulphurCrested]

The standard was changed around 20 years ago to require the insulation. Before that, it wasn't required. Those IEC cables are probably just older than that.

A couple of other things they also did away with are non-moulded plugs supplied with appliances new, and piggy-back plugs.

[askvictor]

Piggy-back is OK (you can still buy piggy-back extension leads), except for the case of a DIY piggy-back plug - this runs the risk of someone wiring two of them together, or a piggy-back plug to a male plug, resulting in danger.