Billions of years of evolution, creating instincts
Humans are born relatively un-developed, compared to most every other creature of the planet. A result of our large brains- we need to be born before being very developed, because we've already reached the limit for how large the babies head can get, before the adult female would be unable to give birth. As a result, newborns are incredibly helpless, needing full time care, and a long time spent as infants and children, being raised by a caregiver who has to invest an incredible amount of time and energy into raising just relatively few children in their lifetime, as compared to a species that raises hundreds of young, or lays thousands of eggs that require no parental care.
Humans have a few reflexes they're born with. Suckling being one, a grasping reflex being another, although there are more. But many other things need to be taught by caregivers, since we're so helpless as infants and being closely raised by caregivers, and have complex social groups that we need to be taught how to navigate.
Many prey species like horses, deer, wild buffalo etc, have a strong instinctive desire drive to get on their feet as soon after they're born as possible, because they're so vulnerable to being hunted, and need to be on their feet to be hidden among the herd, and able to run with the herd - as soon as possible. Any that didn't, would not have survived to pass on their genes, and running with the herd being such an important part of survival for these species, natural selection over time has led to an instinct in young of those species to stand as soon as they can.
Thousands of species have an instinctive fear of a shadow passing overhead - since that shadow is very likely to be a predator. Even humans are born with a startle reflex
It's good question, but the answer isn't that simple as I've tried to briefly explain above, but it's a scientists kind of question, which is great! You'd need to read a lot about evolution and instinctual behaviours to really get to grips with it, and I highly recommend you do! It's fascinating stuff