The evolution of our bodies (from the shape of our bones to the particular sensitivities of our inner ears) such that the equilibrium most-efficient form of locomotion that we perfect by learning by age two is walking on two legs is different from the process by which an individual with that body actually learns to do it. Yes we are wired such that learning the repetitive limb-swinging walking-type of motion is easy, with some species-specific tweaks in tendencies, but all vertebrates are wired like that.

Yes, horses learn to walk in minutes but they have four legs, that's quite a bit easier to figure out. They also aren't born at our massive level of neurological incompleteness.