If you look at top 20, there are exceptions but generally most of these countries have outdoor lifestyles in common. I feel happiness is linked to the simpler things in life and for many people leading urban and suburban lifestyles a lot of them are chasing their tails, being led by the internet on what they should own, how their house should look, how they should dress, how everybody else is richer and leading a better lifestyle than them. The great outdoors is the ultimate leveller, gives you headspace to contemplate life and make you realise how unimportant we really are compared to nature.