It's because the female human body literally cannot hold the child any longer without causing severe physical harm. Pretty much literally every other animal on this planet is born capable of surviving on its own once it is taught to survive. Humans reach this point at around age 5 minimum. Imagine carrying a five year old in your abdomen. Not so appealing, is it?
I mean that is mostly correct, but just to add to that, we actually used to be able to do that. But then once we evolved to a less primitive species, woman's hips had to shrink with things like becoming bipedal or walking on two legs.
So tl;dr we traded birthing toddlers for being advanced humans
They make them cry because it shows that their lungs are healthy enough to be out of the womb (mine almost weren't) and that there's none of that gross fluid in their lungs that was the "water" that breaks before birth
So tl;dr we traded birthing toddlers for being advanced humans
there are people out there whose job it is to make babies cry