You must have ventilation to allow the moisture to leave the property.
Not necessarily, but sure..
Why do people not understand this?
Because they can't see it, and seem wilfully ignorant of being able to feel it. I have an MVHR, and essentially no matter what I do to the internal humidity, it quickly resumes an acceptable moderate level
I have friends whose houses make me feel like I'm suffocating, or drowning, when I walk in and surfaces will be running with moisture
I fear it's more complex for them to understand than "it's cold, shut everything and tape up anything that makes a draught" and "the tumble drier is expensive, but the kids clothes need to dry for school, put them on the heat source"
Lunacy, but have you ever seen a Panorama type program say "look at what happened when we left this damp piece of bread sealed in a Tupperware for 3 weeks, it's pure mould... Now look at this other one we left in a warm dry place with free air movement for 3 weeks; it's crusty as old toenails and not an ounce of mould"
It's basic but no one ever does the education piece. They just tell them things that are anathema: "open the windows"("hell no, it's freezing out and gas is expensive") and "use the tumble drier" ("hell no, electricity is expensive")
If it is poorly insulated, it won't.
Yes, but also poorly ventilated/dehumidified, and excessively moisturised. It's a balance of multiple factors
If every house had an MVHR, was well insulated, had a thermostats set at 19 degrees and was in a good state of repair I don't think this problem would exist
"myriad" means the same as "many" and should not be followed by the word "of" (nor preceded by "a").
There are myriad reasons. There are many reasons.