It's a point that our recent ancestors didn't bathe more often than once a week, and had shirts that had replaceable colours and cuff, so the shirt body could be worn more often. They wore suits pre dry cleaning. Often these clothes were worn by labourers so it wasn't as though nobody was sweating. I once went 3 months without a bath after an accident. You get used to it.

That said, I try to keep up with normal hygene while touring, and it often comes down to a camping ground shower. Not to sure what the folks who don't pay do. I think from the younger ones I have met that they sponge a lot of stop overs from people with showers, like ask people if then can camp in their yard.