Trouble is you have the potential that one day whilst plugging your ev in you find there's no leccy, So investigating the problem you have a look at the board and realise the RCD has tripped. With a second thought you switch it back on, not realising it has tripped because a young member of your family decided to stick a knitting needle in a socket and is still doing so when you switch the RCD back on...
Ok it's a fairly unlikely scenario, but with millions of people in the UK, it can and does happen, and numerous variations of that scenario, which is what makes this set-up potentially dangerous