Preferences arise from the stimuli we are exposed to. ‘We’ in this case refers to people in general. As a result, each individual will have priorities. These do not necessarily need to be justified to anyone else.
Polygamous families operate with different terms of reference to monogamous ones. Boundaries, allegiances and notions of duty will differ accordingly.
In many cases, people stick to socialising with those who share similar values. Some might regard this mode of functioning as limited, standoffish, snobby, provincial or even dull, but life goes on and most of us can choose where we stand.
Others are curious about human nature in general. They want to find out about other cultures and to learn from them. This approach is neither better nor worse than the conservative option.
Paths cross all the time. When folks with diverging attitudes come together, why should anyone make excuses for seeing things the way he or she does?