For most there are reasons why nature does things the way she does. But man isn't always smart enough to know. A baby sees something new. It is picked up, then put straight into the mouth. Learning is aided by sight, sound, touch, and taste.
Same thing is true for animal babies, too.
I never outgrew my own childlike curiosity. As a child, I remember wondering why earthworms would slither out into the middle of the driveway during a rain. When the rain stops, they're trapped. They wither and die. Between birds and insects, their bodies don't last long.