Good parenting/ Bad parenting

So...We're at Kohl's shopping and Emory is zooming ahead 20ft. As he dashes by the manager he brushes her skirt a little and he says, "Oh excuse me!" She stops and compliments us on teaching manners. Gabe and I walk with our head held proudly up feeling very good. This lasts about 20ft until we get to the door of the store and Emory says, "F**k,f**k,f**k, f**k,f**k." (very enthusiastically) We put our heads down, covered our eyes, and tried to get to the car quickly. It was a brief moment in the sun.

Tell me this, why does it take months and months of repetition to get moments of politeness and yet one moment of exclamation after being hit in the head with the shovel is repeated instantly and for months on end. WHY?