[jwilliams]

That and because UK uses a ring circuit, which was seen as a solve for a copper shortage at the time.

Ring circuits generally way higher in power - and a lot more than a single appliance needs or could handle. Hence the need for a fused plug.

The upside is each socket can take a 13A plug (circa 3kW), whereas a standard US socket maxes out closer to 1.8kW.