Hold up - do you mean to tell me that people do not turn off the water while lathering? I've showered this way all my life, is this not the norm?
I’ve had little luck converting friends and family to it, though.
I can understand it for people that like a long shower, maybe.. except that surely it's the water they enjoy rather than just the process, so being there with it off wouldn't be any fun?
Obviously newer/better boilers come up to temperature quicker but you don't always have the luxury of choosing your boiler.
Perhaps you'll be surprised to hear that I also turn off the lights in rooms that I am not in, or that I don't keep cars running when I'm not using them to move around.
Counter-question: why would you ever keep the water running when you're not utilizing the water?