Let's say that every time you tried to visit Facebook, you saw this popup question. Maybe the programmers at Facebook decided that calculus is so important for Facebook users that you can't access the site unless you answer this question correctly. Probably all of them just know calculus, and they're good at it. So for them it's no big deal. Maybe they figure it's no big deal for others since they don't find it hard.
Unless you know how to do calculus, you probably can't answer the question. Probably some percentage of the people reading this can solve the problem. But most of us can't.
How would you feel about yourself and the person at Facebook who decided to make you answer this question if you aren't one of the lucky people who knows how? Would you feel motivated to learn calculus? Would you even know how?
And here is the important point for us as parents: just because I have an expectation of another person doesn't mean that person can meet it.
And just because someone thinks some skill is important for doing well in life doesn't mean another person will just magically have that skill.
I can have an expectation of my child... and it can be a very reasonable one, and very important, and I can even explain to my child over and over again why this thing I'm expecting is important, and that it's necessary that he meets that expectation, so that he can do well in life.
But if there's a huge gap between his current abilities and the expectation, and he doesn't know how to fill that gap... how is he going to feel about himself, about me, and about that expectation I put in front of him? Will he feel motivated?
Back to the math question. See at the bottom there where you can reload the page and get a simpler math problem? You'd probably use that, and feel grateful for the opportunity to do well.
Do you give your child that "out" when you can see that there is a gap between her skills and your expectations? Or do you stick to your guns, believing that if you lower your expectations, she will never learn to do whatever you expect from her?