i think part of it is also that humans have evolved to be scent neutral (to our sense of smell), whereas dogs and other animals, obviously benefit from having some smell to them.
Though you would think maybe the smell gene would've died in humans? Maybe it has.
Have you ever smelled raw human, like a human who's homeless? It smells like a zoo enclosure - animal and humid. Humans 100% have a human odor. It's just not acceptable to smell in general and we keep it tamed down for social and sanitary reasons. Be around someone who hasn't bathed for even 4 days, you will start to smell it.
well it's either wet, which means you should shower, because otherwise that shits going to be really annoying, or it's dry, and it's probably not a big deal anymore. Once you shower that shit is getting cleaned off properly anyway.
Just so we're clear here, sweat is supposed to provide life to bacteria, that's why it stinks.
If you don't use some kind of cleansing agent the bacteria is still there.
It doesn't have to be shampoo, lemon juice/vinegar/rain water can kill bacteria because they're acidic, certain scented and essential oils as well are antimicrobial.
The facts don't change, though. You can't just rinse your hair with tap water for a year and expect nothing to grow in it.