What custard said - you can imagine a company being wary of selling plugs that a user has to wire themselves. I'm sure most of you here are competent at it (Earth wire longer and with more spare than blue, blue longer and more spare than brown etc) but before moulded plugs with new kit was the norm the Consumer Association randomly tested plugs that had been wired by employees of high street retailers.... the results were scary.
Similar concerns about selling 'smart' power sockets to swap for the ones in your wall.
Selling a 'smart' kettle lead as a single unit would sidestep that concern....though it wouldn't make it any more useful.
Biting the hand that feeds IT
