Taking the cynical view, cold fill only machines are cheaper to make. But with hot fill, consider that there's usually a fair amount of cold water going into the machine before the hot water comes through the pipe. And it's only the main wash that uses hot water - all the rinses are cold water. Unless you're doing 60 deg or 90 deg washes, a cold water fill shouldn't take too much longer than a hot fill. Remember that with a hot fill, you're still having to heat up the equal amount of cold water in your heating system, so the only saving with a hot water fill isn't money, it's just the extra time. We start our machine just before going to bed. That way, stuff is ready next morning, and we are never waiting for it to finish.