I really don’t understand people like that. Anyone who’s ever gotten a bad case of the flu and felt so weak and sick they had to skip showering knows the result. You feel sticky and gross, just after a single day of no soap and water. How some folks can go like that indefinitely is beyond me.
Sort of depends how oily and sweaty your skin is.
My MIL is a doctor and scrupulously clean and well-groomed. She has very dry skin and takes one lukewarm bath, with bath oil, every week.
Before adolescence, children aren’t smelly. The children in my daughter’s fifth grade less express disgust that anyone might shower less than once, or maybe even twice daily, and it has to be a shower, because a bath is sitting in your own soup. Peer pressure. They have no idea that my dry-skinned daughter takes a bath when she feels like it, which is maybe every ten days or so.
And yes, she is almost at the age when I bought my older children deodorant and said, you need to start showering a whole lot more often. But not yet.