Tim Lamb was thinking very hard :
And quite right too. The switch contacts are designed to break the current
cleanly. The pin contacts may suffer a series of arcs leading to pitting and
degradation. In the worst case heating such that the Beryllium copper
contacts lose their *spring*.

Were the sockets not designed to break the current, then all sockets
would be fitted with switches.

Worst case is domestic staff switching off kettles by lifting the jug from
the base as you might from a kitchen range!

I do that too. They have a switch in the base to swith the supply when
the kettle is lifted. Even if the base switch does eventually fail, by
then the kettle will need to be replaced. They are not expensive these
days.