It’s a pros and cons thing. The pros in this case are our upright posture with narrower hips that let us cover long distances more efficiently than most of the rest of the animal kingdom. We can even do things like carry food to eat while walking, which something like an antelope would struggle with. Then a second pro is the whole big brain thing. These two factors did let us take over most of the planet over the course thousands of years, pretty quick work, really.

Then the cons are high mortality in birth, and taking something like 10 years after that risky birth to become even semi-functional at a practical level.