I have the answer to your bolded question.
I've lived in many parts of the country & have experienced all forms of humidity or lack there of. I grew up in a couple of the Great Lakes States. I remember sometimes at 70* or lower, you could just sit or lie still & pour sweat. The less wind on a humid day, the worse it was. Dehumidifiers were very common. I can remember dumping that thing twice a day. The thought of a humidifier would be ridiculous. They don't call Minnesota "Land of 10,000 Lakes" for nothing.
I've lived in Southern California right near the beach where although humid, the ocean breezes usually did a pretty good job of keeping the air moving & lessening the humidity. Open windows were usually enough to keep the worst off. Same with Washington State. Loads of humidity & drizzling rain, but the temperatures are usually moderate & same thing: close to the ocean you get ocean breezes. Both places also benefit from Dehumidifiers.
Now I'm in Montana where the air is dry. Especially in the Winter when natural gas heat dries it out horribly. I keep a large pan of water in my furnace for this reason, which I refill every few days in the Winter. Without it I'd be snapping everything I touched. Carpet makes It worse. Many people have humidifiers & use them regularly in the Winter.
Another thing is young children when they have colds or flu & their noses/sinuses are plugged up. A humidifier in a closed room helps them to breath & sleep better. They even make them looking like cartoon characters or cheery cute animals.