Because humans are born at an earlier stage of development and evolved as a species with the mother carrying the young in her arms for transportation, protection, and nursing (hence the chest-mounted udders rather than at the lower abdomen like other species). Human ancestors lived in the trees for millions of years before the species started migrating to the ground to roam the African plains. Species like goats, horses, deer, and other ungulates are prey species and need to be able to walk and run as soon as possible after birth in order to have any chance of escaping predators. They need to be able to fend for themselves because nobody can carry them and they can't climb trees. Now, other species like mice, squirrels, raccoons, foxes, bears, etc. make nests or dens where the young will be protected, so when they're newborn they are very much helpless and can't walk or anything for quite some time because the protection of the home allows that helplessness.
Short answer to your question: evolution.