Technically speaking, everyone doesn't need to wear deodorant. Researchers have discovered that a particular gene is responsible for producing certain acids in sweat. Bacteria feeds upon these acids, breaking down into other acids, which emit unpleasant body odor. Those people who lack this gene, which include a small number of individuals with a European background but a high number of people of East Asian descent, do not really generate armpit odor and therefore don't have a real need for deodorant. Proper hygiene, including daily bathing, may, however, still be required to avoid smelly pits.
More information about body odor:
First, I love this article, but I'd like to share my experience with smell. I am a runner and I do work out every day. This deodornat article may not be entirely correct. Body odor is related to what you eat every day because the body reacts to chemicals within the food you consume. For example, if you try a vegetable diet every day, you will have less body odor than when eating a lot of meat, fish or poultry.
Also, people who exercise regularly tend have less smell than those who do not. Everyone sweats but it is the severity of the smell that makes people uncomfortable.