Why every time people say you are really smart,handsome,etc when you're young

I've been thinking lately why everyone keep lying to their kids about them. They tell them their nice,smart etc...let's face it not everyone is handsome and smart and all those qualities. I am not envying them,I just have the feeling that when we were kids we were lied a lot and raised our expectations.For example my parents told me I am very smart and really handsome and I grew up with that and now I realized I am not that smart or handsome. Is just that simple problem that when you're young you have your head pumped up with all those crazy things and you have dreams and you hope for a prince/princess in your life and suddenly when you reach your 20's BANG----> reality check...life suck's. The hole purpose of this post is that I think parents shouldn't lie their kids that much,I am not saying tell your kids their ugly or stupid .. encourage them of course but make it in a way to prepare it for the future so when they grow up they are prepared for the reality and not for a dream..