Can‘t you how tired your boy is

Can‘t you how tired your boy is
Once there was an old farmer, with a horse which was almost as old as himself. He set out one morning with his young son, to sell the horse before it died. Father and son walked, because the farmer did not want the horse to be too tired.
They met two men on the road who said, ‘Why are you walking, farmer? You have a horse. It’s a long way to the market.’ The farmer knew that this was true, so he rode on the horse, while his son walked.
Then they met two old ladies. ‘What are you doing up there, farmer? Can’t you see how tired your boy is?’ So the farmer got down, and his son rode instead.
里的Can‘t you ( ) how tired your boy is
为什么要用see而不是notice