I can understand why you might presume it's shallowness but it's really a type of etiquette. Similar to offering a handshake. I'm Scottish rather than American

I can understand why you might presume it's shallowness but it's really a type of etiquette. Similar to offering a handshake. I'm Scottish rather than American but here babies are often encouraged to smile at family and friends. It's exactly the same as teaching please and thank you