My girlfriend finds showering and bathing extremely painful due to several very severe skin conditions. She’s also allergic to almost every deodorant that doesn’t cost a ridiculous amount. She doesn’t sweat a whole lot so it’s usually not an issue, and can get away with only one shower a week usually. Her conditions are pretty rare so I’m not saying everyone who doesn’t shower regularly has what she has, but there might be factors at play for some that give them legitimate reason not to shower. Or it could just be laziness