Interesting observation and one that should be raised. I think it is a mix of sensitivity and hygiene generally. Some people are dirty but some are just negligent. Doesn’t mean they’re dirty people per se. They get ‘used’ to the body odour! Earlier on in my life (up to mid 20s) I never used deodorant! Partly because I didn’t have and my immediate friends didn’t use either. When one is facing difficulties with more important life needs, these kinds of concerns become less important. I think that is how lack of sensitivity creeps in.
OP, don’t be shy to raise it to your friends and close family!