I think it's because it's much easier to get warm in winter than to get cool in summer. It takes much less effort and organising.... you simply put on woolly clothes.

People who live in perpetual summers, like us here in the semi-tropics, have to take thought for ways to keep our temps down ALL the time, whether we're working or playing. We have to drive long distances to beaches and pools; run air-conditioning 24/7; wear shady hats and avoid over-exertion in the sun; constantly clean ourselves of sweat and grime; fight bugs and flying insects; endure massively destructive summer storms; and face the threat of raging bushfires that destroy and kill almost every year. It's all a damn nuisance.

In cold climates, you can choose to be more active or you can choose to stay indoors, and either way, you can be comfortable. And I think the weather is somewhat more predictable in cold countries. They've had generations to arrange their living styles to allow for the cold. In the tropics, we never know from year to year what we'll get.

That's enough to make anyone "unhappy".