So where has culture and art come from

Why do we choose to choose to be monogamous instead of polygamous like our programming dictates 
And why do we go against our programming to stay with our mate when we feel attraction to other people
Why do we make such unproductive choices?
Why do things that we know are bad for us and that we shouldn't do?

Because the human mind loves finding shapes, patterns, habits, categories, and order in chaos. Physical patterns like colors, lines, and borders, lifestyle patterns like daily schedules and habits, categorizing things as 'good' and 'bad', 'should' and 'should not', and so on.

It's why we try to find faces and objects in clouds, why we only step on certain floor tiles while avoiding others, and why we reflexively stop and count things when we see them in large groups - because we need to put an order to them.

It's just how we're programmed to think.