As a child you sometimes sit by the window and wait for mom and dad to get home.
You do that because you probably miss them and want to share your day with them.
As A baby, you probably do that for the same reasons, though subconsciously and with less verbal communication involved.
But how about if you’re a dog?
Dogs are often very excited to see their humans come home after a long day.
Put A baby and a dog together when daddy comes home and you’ve got the recipe for cuteness!