In general, crossculturally courtesy language (please, thank you, may I, etc...) and much greeting and leave taking ceremony is to establish space, terratory, and awareness. It distances a person from another. Saying please and thank you in effect establishes ownership, change of ownership, or retention of ownership, especially when dealing with actual objects or actions regarding space and terratory. Greeting and leave taking ceremony in effect establish presence and permissions for occupancy of space and terratory.
Oft times this is based on a cline of family-group-community or peer-superior-superior group. For example in band level societies lack most of what we would consider basic courtesy language is suspended in fact some languages to not have a way to express please and thank you. Think of it much like a close family who suspends much of the same courtesy language because the 'property/space/terratory' is shared. When a mother/father forces the child to please and thank you within the confines of the family, it is often it s not to establish these line but to teach their children that there are lines when they leave the nest.
The more striated the society becomes the more important courtesy language becomes, especially among cultures that have clearly delineated economic classes and or social classes.
So I would suggest that most language has a utilitarian function in at least a secondary or terciary manner. Even empahtics, interjections, and poetry have their utilitarian functions. One reads or writes poetry to express oneself and thereby gaining some cathartic advantage. Same with the escapism of movies or the general release of frustration associated with emphatics.