Climate definitely has an influence on the speed that mould can appear. In Auckland things can go mouldy very quickly, whereas when we lived in less humid Canterbury you would be looking at a couple of weeks rather than a couple of days.
Personally I think the point about rental houses in very valid. Generally, people who invest in properties to improve them, are doing so for their own personal comfort and not for renting to someone else. Therefore damp and mould tends to be more of an issue in rentals.
We've lived in several different houses in the last 4 years, and 4 of those houses were each less than 5 years old but still with single-glazing, and each and everyone of them has developed mould around the windows. To keep it at bay requires constant attention and effort from about early May to late September. In Canterbury all I needed to do was wipe all the windows, and especially the window frames down every morning with towels and ventilate the rooms for a bit. Here in Auckland I find this is especially important, as is my routine of cleaning the window frames and drainage channel at the bottom every 2 weeks with bleach. I've found that if I don't do this, the curtains or blinds begin to get covered in mould. Quite frankly, I find it a time consuming pain in the ****.
Bathrooms I've found less problematic, because all but one house we've lived in has had an extractor fan in the bathroom. That's not to say that we don't have to work at preventing mould, but it doesn't end up overrunning the place. What we do have problems with is getting towels and non-tumbledryable washing dry because it begins to smell musty within a couple of hours unless we're careful and once items have mould spores in them, it's all but impossible to eradicate them....which is a problem for me as I'm allergic to mould spores.
Also, I've got friends who have had things go mouldy in wardrobes, under stair cupboards and under their beds pretty much every winter. They live in pre-1990 houses which don't have any insulation at all AFAIK.
Of course, as you said, you could just leave your windows open all the time so the difference between the outside and indoor air temperature is less, which will reduce condensation. However, this is not at all healthy or a pleasant way to live during cold weather and it would be far better to have a well insulated, heated dry house so mould spores don't reproduce in the first place.