...and keep the same clothes on for some days...
I take it that you people change clothes twice every day? I usually wear the same clothes for a couple of days. I'm not that filthy that my shirt becomes unusable after 12 hours of watching TV... If I'm sweating a lot for some reason (like working etc), then of course I chance clothes and shower after that. And underwear (if, for some reason, I'm wearing them) I chance frequently.
And I don't necessarily shower every day. I go to sauna + shower 2 times a week, and plus a couple of additional showers to that. Quite enough washing for me.
And this is in Finland, where clean water is in abundance... We have those lovely lakes. We don't even drink bottled water much here. But I hear in some countries the drink nothing else.
Italy of course is another matter. It's a hot climate and surrounded by the Mediterranean. And that particular sea, as we all know, is shallow puddle of filth... So its not surprising they have a water shortage. That using the same bathwater for a week thing is disgusting. Why don't they use a sponge to scrub themselves clean? Uses a lot less water with good results.