There are a lot of reasons. Some people may bathe but have a medical condition that affects body odor so it seems like they don't. Some people cannot afford to spend a lot on their water bill and bathe less often. Other people are simply lazy and don't want to be bothered. Finally, some people may honestly have no idea they smell.
Some people dont realize they smell but others do and thus they make fun of that person you could smell masty and i not say anything so does it really matter some people cant afford to pay their bills and some can it doesnt matter what you look or smell like where all human so dont be like eeww he smells like toilet thats just rude everyone has their flaws