It largely does, in humans’ close relatives. Male chimps are about 50% larger than female chimps by weight; the same goes for bonobos. The same is broadly true in most mammals, with a few exceptions (notably rabbits, who are actually more closely related to humans than a lot of mammals).
But to answer your question: testosterone is just a signaling molecule. It doesn’t, inherently, make you larger or stronger, it just tells your cells that it’s there (which causes them to start processes that do). Evolution can change the response to such signals in response to a variety of pressures.
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