The historical reason why is that UK homes were wired early in history for lighting with a ring circuit going throughout the house, and this was also literally set in stone so impractical to phase out for a long time.

So the regulations had to allow one 50A (for example, I don’t know the actual numbers) fuse supplying an unknown number of outlets and devices, rather than requiring one circuit per small area. Such a large fuse will happily let your radio malfunction and start on fire, so local, smaller fuses are necessary.

In other areas a 10A fuse (for example) on a circuit that only goes to one room or one appliance is enough to protect from overloading the circuit as well as most dangerous malfunctions of one device.