I would think it's because of the different current specifications. In the UK most electrical outlets are on ring circuits that are limited to 32A - that's a w

I would think it's because of the different current specifications. In the UK most electrical outlets are on ring circuits that are limited to 32A - that's a whopping 7.5kW. Fuses in the plugs of specific appliances provide additional protection with 13A being the largest (3kW) required. Bathroom outlets are required to have a separate transformer that isolates ground. This prevents the possibility of any electric shock from a short to earth. The current the isolated transformer provides is limited so connecting a regular appliance cannot be allowed.