It's really stupid though. The old English (and even new one) in particular take up enough space for several plugs. What do the plugs for English washer/dryers look like? They the size of a brick?
All UK domestic appliances use the same plug - so, your iPhone charger has the same plug as a clothes dryer.
Before WW2 the UK had lots of different plugs, using round brass rod pins. There were 3 sizes - 2 amp, 5 amp and 15 amp, and the sockets would be installed on appropriate sized circuits.
After the war, considerable rebuilding was needed, but there was a severe shortage if metal. Engineers worked out that the conventional wiring scheme where a single panel circuit feeds one receptacle or a few in a chain fashion was inefficient in terms of wiring requirement. So they standardised a ring connection, where a wire from the panel loops around a bunch of circuits and back to the panel.
The disadvantage with the ring configuration was that it meant huge amounts of current available at each receptacle. This required that individual plugs have fuses in them, to prevent individual appliance leads from fire. Hence, the plugs had to be big enough to accommodate a fuse.
At the same time, the decision was made to standardised on a single plug size. The previous multi-size arrangement was inconvenient and misuse of adaptors was dangerous and a major cause of fire. At the same time electric space heating was the new fad - nat gas hadn't been invented, and coal fires were deemed "old technology". The plugs were deliberately over-engineered in order to safely support space heating loads for continuous use.
A number of Commonwealth countries have copied one of the British standards - some, the old unfused round plugs (south Africa, India), some the modern square pin ones.
