My city is in the middle of the worst drought in recorded history. My showers are typically under 2 minutes and I have to shower with a bucket to catch otherwise wasted water to use to flush the toilet. I also shut the water down when I am wet enough so I can scrub myself without having unneeded water flowing then start it back up to rinse.
Plus, water is damn expensive!
Who here really has the time to stand, think and waste in the shower?
It can help significantly. Having a big reservoir that can hold water during dry years and then collect water during wet years is really good. It is expensive and requires land and infrastructure but it can make it possible to not need water restrictions during dry times.