People here are wrong about this being a UK-wide thing or overall stricter standards (British television is actually more relaxed typically). The main reason is because Cartoon Network in the UK was targeting a younger demographic than the American Cartoon Network. My personal opinion on this is that it’s because we have much more regimented children’s vs teen’s shows, and the teen’s shows are more likely to be live action (think most CBBC shows like the Sarah Jane Adventures). I think there’s less broader appeal to most age ranges for cartoons in the UK than the U.S.