for 20 years i showered every day, i felt icky at night if i didn't
but i gradually got more and more lazy, it still felt icky at night, but i put up with it
now i'm used to it, i dont feel icky any more, i feel fine. i feel clean i feel fresh, i shower on every 4th day. Mainly because my hair gets that greasy build-up, which i tell everybody is gel/wax.
You get used to it, it saves water, money, time and effort
Obviously if i get dirty, or sweated alot on that day i would shower, its not set rule really. Who says you MUST shower every day. I shower when i feel the need, when i feel dirty.