It's part of Norwegian culture:
"Cabins are a big deal here. A big deal. People love cabins, and it seems like every Norwegian family has a small place either up in the mountains or down by a fjord where they spend their weekends.
But, oh, Americans, don’t get any crazy ideas in your head. We’re not talking about plush villa kinds of cabins. No, no. We’re basically talking about formidable wooden tents. Bathrooms? Running water? Stoves? That junk is for people who aren’t Norwegian! A Norwegian cabin need only be snow-proof lodging heated by a wood burning stove. And sometimes, if you’re really lucky, there’s a sauna."
I am currently sitting in my "hytte" at the Oslo fjord, looking out at the water beneath me. We have have a bathroom with hot and cold running water and a fully equipped kitchen. It is still ei hytte, in the meaning summer house. It is not unusual. So the Norwegian hytte anything form a wooden tent to second homes with all facilities.