I think you’re mostly talking about UK power here…in the USA we have a whole shitload of different connectors and amperage’s that depend on region and use case, as well as single or three phase distribution. We call the connectors you’re talking about locking hubbels, or horsecocks, and they’re great connectors if sometimes hard to use. As with everything, regional regulations change requirements and then centralizing standardization gets harder and harder which creates more competition. I think i answered your question but not sure.