Why do we expect so much from our children?

After talking with a good friend this week, the inside of my mind resembled a pin ball machine each thought building on the next in such fast precession that I finally broke down and decided I HAVE TO GET THESE THOUGHTS OUT OF MY HEAD, if for no other reason than to free up space for more...
Being a single mother of a brilliant(biased opinion) five year old boy, I have come to realize how much I truly expect out of him. But, when I look at the example I have modeled for him I myself am unable to obtain any of these same expectations. I have also noticed this is how our society operates as a whole!
Why do we expect so much from our children?
Why do we expect them to laugh all the time, take naps obediently, always want to share and use kind words? Why do we also expect them to never get cranky, not be hyper and eat everything we put before them? Why do we expect them to be able to handle a visit to the doctor or the dentist without being afraid with minimal amounts of crying? Why do we expect them to bounce back from a traumatic event so quickly?
Who told us to expect all these things from our children? Is this what our parents also expected out of us when we were young?
And, why do we feel the need to punish them when they are unable to meet this goal?
Yes, I do believe God put parents on the earth to lovingly and patiently raise their children up, but it seems to me that we expect so much from them, but let ourselves off the hook, almost always.
So of course I had to try and look at this through a child's eyes and what they possibly might be observing when they watch us.
As a parent or adults in general, these are a few scenario's that came to mind...
While driving someone cut's you off, how often do we tell our children, "see honey I'm just letting them cut in front of me because we really need to share the road and notice how I used such kind words"....never. But we expect children to innately want to share what is most precious to them and to be spouting kind words from their mouth, endlessly.
Imagine an adult who just had three cups of coffee, it's late and they are starting to get a little hyper because of the craziness of life or lack of sleep, can you even imagine the response if someone told them to "settle down stop being so hyper" or every time we got mad or were cranky, to have to sit in the corner or take a time out, we would just throw another fit, just like our children tend to do.
The only real difference I see when it comes to adults in this area, is that sometimes we show a little more tact before we throw our tantrum. We make excuses in our mind to make it OK, but when a child tries to reason with us we discount their excuse almost immediately. What a double standard we present.
I honestly feel like we should let our nation be run by our children, since we already expect more from them then we do from adults and politicians alike. Through all our misleading examples, they are more innately honest, their motives are more pure, they see the good in people just because...
Freely giving of their love....
I want to be more like our children....and maybe for a change see what they can teach me...