They're used to couple equipment a lot.
Lawn mowers and garden equipment for example. A short cable dangles off the mower with a plug and you have lead with a socket.
BS1363 isn't very suitable for that kinda thing because it can't easily be pulled apart.
Often irish garden equipement comes with Schuko plugs and a BS1363 (with RCD) plug to a tough rubber schuko socket.
If for some reason you need to quickly disconnect BS1363 it just doesn't happen.. they won't pull out of a socket unless you grip the plug and pull.
They also limit what can be plugged into a "coupling" to the applience only.
