The need for resistance training for muscle growth is mostly a human trait. With appropriate genes, simply growing muscle without the training is not only possible, but takes fewer calories, so it is much more efficient and preferable by other species.
Exercise for the sake of exercise burns up a lot of calories which in other animals is best preserved for acquiring food, reproducing, etc. Humans engage in muscle building as a result of our societal evolution from that of hunter-gatherers where we were just like other animals of today. Division of labor has made food acquisition the least of our worries. So, we now have dedicated plenty of time and resources to working out to impress people (or most likely ourselves).