Why is homework so hard for a 10 year old?

And why is there so much of it? My ten year old has about three hours of homework every night. Now I'm sure this is for several reasons:

1) He takes forever to actually focus on it
2) He gets at least three pages front and back every night
3) He is VERY easily distracted (look a squirrel!)

And the most fun part is when I go to check it and it's wrong...then the temper tantrums begin!
Oh joy! Just want I have been dying to deal with since I got off work, battled traffic on the 12 mile drive home that takes 30 mins, and cooked dinner. He swears he's not wrong, there is no way it could be wrong, cause he did it and doggone it, it's right!!!
Then the AH-HA moment comes when he realizes his mistake. His voice gets softer (well, softer from the high pitched squeal he was earlier screaming at me in) and he says, "oh, I guess the answer is 3,452."

And the funniest part of all...

I remember being JUST LIKE HIM!