Art is pointless, because it has to be
Why would a prehistoric hunter-gatherer, after a long tiring day of hunting-gathering and dodging dangers, come home only to throw up hand prints on the cave walls?
The honest answer is that we don’t have a clue. Its apparent lack of usefulness (at least as far as we are concerned) is enough to qualify it as artistic expression.
Art is mostly useless, and that’s okay
With the benefit of hindsight, it may be possible to find some utility in art. Perhaps you can look back to a time when a film or a song helped a social justice cause or acted as propaganda for an evil regime, but chances are that is not why it was created. If you were to go back in time and ask the artist why he/she created it (before the “use” of this piece of art was discovered), it’s unlikely that you would get a satisfactory answer. What makes art compelling is that it cannot be linked to anything useful. It’s a feature, not a bug.
Art makes money, but that’s not what it’s for
The concept of art as a way to make a living is relatively modern. Sure, people in the past derived income from it, but that was incidental. Traveling musicians did not sell concert tickets or records but were provided food and lodging by their hosts. Poets and sculptors were cared for by wealthy patrons, unless they were wealthy themselves.
The art somehow came into existence, then people paid to enjoy it. It did not come about as a result of upfront investment in music lessons, painting classes, and promotional marketing. Only in modern times have we come up with the notion of a professional artist, who creates art to make a living. The problem with this mindset, aside from the question of the profession being a viable one, is that it assigns a purpose to something that has none.
Art can be entertaining, but that’s not what it’s for
Works of art can certainly be entertaining enough to justify the existence of an industry where people, both producers and consumers, spend significant amounts of money. But once again, that demand cannot be the primary purpose. If the demand dries up, will the same happen to the supply?
Sure, many artists who work in the entertainment industry will be forced to switch careers. But it is unlikely that all of them will quit art altogether just because they cannot make a living from it. Those who never made money from it will, of course, go on doing what they do regardless. Financial success is, at best, the oil that greases the wheels, not the spark that lights the flame.
Art is in the eye of the beholder
Let us say that in some time in the distant future, we figure out what all those hand prints in the cave mean. Maybe it was a routine religious ritual, or a primitive form of record-keeping. In that case, it will cease to become art. It will simply be another object of interest to archeologists and anthropologists. Discovering the point of it will remove it froom the realm of artistic expression. Therefore, art is not only useless but also subjective.
Art vs. propaganda
Propaganda, by definition, cannot be art. For any kind of propaganda, there exists clear motivation, which usually has something to do with converting people to a particular way of thinking. The fact that some propaganda can be dressed up as art should not lead to confusing one with the other.
On a side note, propaganda is not necessarily false or unethical. Refering to something as propaganda has negative connotations, suggesting that it must be full of twisted half-truths, if not outright lies. Propaganda is simply a version of reality filtered through a biased perspective. It can be used get people to enable genocides or quit smoking.
Why keep it around?
The point is that art, at least from the perspective of its human observers, really is pointless. Then why does it need to exist? If that question can be truly answered, I believe the need for art will disappear. Until then, we can only wonder. However, we can assume that the need does exist, if only because people believe that it does, and that is enough to justify the effort and expense incurred by art.
State-of-the-art
Today, throwing up hand prints on walls is only expected of little children, and even then not usually considered acceptable behavior. Adults are expected to sit in their designated places and enjoy entertainment prepared for them by professional artists. When did so much of art become so formulaic and predictable? It’s hard to say exactly when, but it is a reflection of broader changes in humanity.
This does not necessarily mean that this process cannot produce art. An artist should be capable of producing art regardless of incentives, since art is useless and cannot be tied to anything useful. However, this has caused an uptick in the amount of bland filler imitations of art, which might drown out the real thing if given enough room.