The term "culture" is a concept that has developed in the last few hundred years as a way to explain different behaviors between groups of people.
The psalmist knows that God's people are often tempted to take God's grace for granted; we are often tempted to see God's grace as cheap and fail to recognize what it cost for God to forgive his people. We often grow comfortable in our sin because we think that since we are God's people, and he has made unconditional promises to us, then we no longer need to repent; we no longer need to confess our sin. We no longer need to fear God.
There are 12 Days of Christmas contests on the radio, 12 Days of Christmas sales at the mall, 12 Days of Christmas charity drives, and, of course, that very long song.