I have been involved in many of these types of discussions, and I'm convinced that we are not experiencing the same temperatures when we set our thermostats to the same temperature. If I set mine any lower than 77°F, I would freeze to death. But many people here set theirs to below 70°F.
I have a few hypotheses.
Apparently AC units can really only make the temperature about 20-25°F degrees colder than the outside ambient temperature. It is over 100°F in my area almost every day from June to mid September, so any temperature below about 78°F just means your AC is on 100% of the time. This is removing moisture from the air, making it feel colder.
My thermostat is right next to my garage door, which is not insulated. This is probably where the majority of heat enters the house. So the thermostat thinks it is warmer than it is. Other people might be in similar or opposite situations and need to set their thermostats to account for that.
People's AC units are not actually cooling anywhere near those temperatures. The unit is just on 100% of the time at those temperatures, and they could realistically increase the temperature a great deal and get the same results.
Humidity.
Some people's AC units/thermometers just suck. 65°F on their unit actually gets the space to the same temperature as 75°F on my unit.
Most thermostats do require calibration, and nobody has time for that. This has a similar effect to your second point. Proper air flow (or lack thereof) throughout the home is also important.
Sunlight makes a huge difference. A temperature that feels comfortable at night may not feel comfortable at noon in a home with a lot of natural light. Same as a sunny vs a cloudy day, indoors or outdoors.
Men and women have drastically different tolerances for comfortable room temperature. In general, non-menopausal women tend to appreciate a slightly warmer room than men. This plays out in office spaces all over the world, with many women running space heaters under their desks.
Clothing obviously makes a huge difference. Some people prefer to dress for their desired temperature; others prefer to dress for their physical comfort and let the HVAC balance things out accordingly.
Medical conditions and medications and diet can all drastically affect one's body heat output. For example, anything that boosts serotonin is likely to make one run hot. Stimulants will constrict blood vessels and make one cold, especially in the extremities. And we all know what alcohol does (dilates blood vessels, allowing more heat to escape the body, lowering one's body temperature despite actually making them feel warmer). Blood sugar levels make a difference. The list is endless.
But it's interesting that most of your thought process went into how HVAC systems and humidity work, versus the simple fact that the people themselves are just drastically different (see points 3 through 5).
My thermostat is right next to my garage door, which is not insulated. This is probably where the majority of heat enters the house. So the thermostat thinks it is warmer than it is.
I've got an Ecobee thermostat and they sell little temperature sensors that you can place anywhere in your house. You can configure which sensors are used at which time - for example I have a sensor in my bedroom, and configured it to only look at the bedroom temperature overnight. If you select multiple sensors, it averages them.
Yeah, those are all good points and certainly factor in. There are objective studies about human comfort preferences used for building design. I expect OPs question is a roundabout way to ultimately ask about comfort preferences.
Studies done on temperature preferences are also biased (like medicine studies or calorie recommendations). Office building studies were based largely on the preferences of white men. Not even accounting for individual preferences someone being in a different "category" (i.e. gender) may also influence at what temperature they are most comfortable.