Upgrade, Attaking and Defence of King

During loading of game on welcome screen, A message shows that "King is bigger than giants his capability of taking dark elixir make him bigger and strong then giants".
My question is-

1. If king is like giants then why he didn't prefer defences?
2. Second thing, when he is a living unit, then why he needs builder to upgrade himself?
3. If he needs a builder to upgrade himself then why he sleeps on his base, why he didn't attacks like other troops while upgrading?
4. Third thing - When he has it's range, why he didn't recognise enemy troops, like clan troops?