My nephew was straight up adorable from the moment he was born. People doted on him left and right. He was a personable, polite little boy (beyond his years so it stood out) and wait staff etc would take time to say hello, compliment his parents and maybe give him a treat.

Then he got that little bit older and his baby brother was born. The attention shifted away from him. You could see him try to interact with people in the same way, and when he didn't get the same reaction a little light left his eyes. Don't get me wrong, he's a great little teenager now and it hasn't affected him. But there was a short period of time where he was a sweet little innocent and the world rewarded him for it. The rewards go away, and sometimes without them I think the child stops exhibiting the behaviour.

Interesting thought op.

Edit for typos