I think a big part of why UK washing machines aren't in bathrooms is our electrical regs, which don't allow plug sockets within three metres of a bath or shower

I think a big part of why UK washing machines aren't in bathrooms is our electrical regs, which don't allow plug sockets within three metres of a bath or shower. Most UK bathrooms aren't big enough for that, so you end up having to do awkward workarounds like giving them a hardwired connection and/or boxing the machine into a cupboard. (I used to own a flat where the only space to put the washing machine was the bathroom and had to get it boxed in...)