Why do we fear rejection and appreciate appraise?

As babies we thought the world revolved around us, praise, praise, praise. We get old enough to really like the praise, and all of a sudden (or it seemed like) we start being rejected. "Don't throw your food on the floor (mom, you use to laugh when I did it.) Don't walk in here with mud on your feet ( mom, you use to take pictures of my foot prints). Close your mouth while chewing your food< (mom)