are we humans? or are we dancers?

one of the first lessons that they teach you when you are learning to dance any social dance is the following:
practice! dance with as many people you can, have a lot of different dance experience and learn with all of them. Therefore, it is not correct and you must avoid the attachment to only one partner. Indeed you accumulate errors and get use to the other person way to dancing. The professionals claim that you must dance with other people, even if you have a stable partner. they consider stupid and counterproductive for you evolution to get stuck with only one follower or leader.
Now, that is in the dance floor... but isn't it the world a huge dance salon. Aren't we learning how to live or how to dance. If this analogy is truth, and we are dancers, then why all this social pressure to keep only one partner? why is bad to enjoy different songs with different people.
Evolutionary the system of a couple has given advantage to the survivor of the offspring. Socially we had created so many rules to keep everything under control that it looks that we can only dance one style per time. Are we limiting ourselfs superimposing external rules?
perhaps in case we found a great dancer, the one that we love to dance with is the event that keep us away of the desire to try other styles.