Truth be told, there's quite a bit of data to indicate that unless you're working outdoors at a manual labor job, have worse-than-average BO or running a gym where you sweat for hours at a stretch, it is healthier for humans today to only shower twice a week. And it is undisputedly healthier for most hair types to NOT shampoo and wash the hell out of it more than than.
It is often going to be visually noticeable if your metric of comparison are people who shower obsessively and coat themselves in makeup or product, but it doesn't necessarily mean that the person is filthy or smelly. The only stuff you really NEED to be washing daily is your face, your hands, and your junk/ass. Though bidets still haven't really taken off well in the States. :/