Rousseau is very idealistic and theoretical in his approach. It would be nice if he was right, but we're far from ever experiencing such a state.

[ It's not that Miach doesn't want people to be happy - she just doesn't see a way towards it that isn't plastered with falsehoods. ]

Hobbes meanwhile holds with what we can quantifiably experience. His human nature shines through in every society we find world-wide, causing them to be ever-inefficient methods of solving a problem that is completely inherent to mankind.