Copying and pasting my answer from the same question just 2 weeks ago:

How do you know they all weren't wearing it?

There are a lot of people who do wear it but continue to smell because of underlying medical conditions. For example, fruity smelling body odor can indicate diabetes. People with a rare genetic condition called Trimethylaminuria can smell strongly of fish. It all depends on what bacteria (which outnumber your own body cells by 10 to 1 even though they are only 2% of your body mass) and what balance of enzymes you may or may not have.

Reducing perspiration can and often does help, concealing the odor with different ones can help, but sometimes people's bodies just aren't right for whatever mass produced product they have bought. Sometimes that can be fixed with medication. Sometimes it can't.

https://kbin.social/m/asklemmy@lemmy.ml/t/638513/-/comment/3647566