I Think I'm Going Crazy

Why can`t the whales fly too?
And why are ants so small?
Green is not a colour,
So why are giraffes so tall?

Books are all for eating,
And elephants can`t swim in glass,
Are nails really made of hair?
Or is it just a farce?

Snails move too slowly,
And get crushed in to the ground.
Why don`t they just grow wings?
Then they can fly around!

A tortoise doesn`t have ears,
And yet of course it can hear!
I`m really quite intelligent,
So what am I doing here?