It happens with almost anything you can think of. 3G and 4G in phones, broadband internet speeds, small cars, fashion :), etc etc. It just isn't economical to have a huge amount of water be kept really hot all the time. Plus there are leaks, danger of the thing blowing, it taking up space, etc. Energy (natural gas, oil and electricity) is very cheap in the US at the moment so wasteful cheap technologies are the norm but it won't be that way for long. Won't happen overnight but if it happened in the rest of the world it will happen in the US too, it always does.