Filmmakers can use the movie they make as pure artistic expression without also offering something of value to the audience, though it's not advised. Of the many ways a filmmaker can make a movie, the best way is to tell a story in it. Including a story in a film shows the filmmaker cares about the audience and their needs. Along with that comes some slack. The audience will feel they can trust this filmmaker and give him or her the benefit of the doubt.

If you don't include a story in your movie, the audience will be searching frantically for things to keep them occupied and their need for entertainment satiated. So instead of telling a story in your movie to give them something to occupy their conscious mind, they will consciously be picking apart your film and probably won't find it that compelling.

Acting

Acting is just being, and since everybody in their life does that on a daily basis they all feel they know what good acting and bad acting is. Not only will they be extra finicky when it comes to the acting styles, they will also demand that every acting moment be interesting. Suddenly an audience member may arbitrarily decide they don't like one of the actors and no matter what they do they just won't believe it. There's no logic behind it, they just have this negative feeling inside them and they are projecting it on this actors face. If you don't have a story that holds people's interest by way of wanting to know what happens next, the audience will have to fill in the rest.

Cinematography

In a movie where the acting isn't that good and there is no story being told, these pictures on the screen better be very appealing. Since the audience has nothing else to do, it they will have lots of time to analyze every aspect of your shots. They'll notice, or think they notice, drastic difference in between shots that make it seem like you are an amateur. The grain will be slightly more than the frames before it, or the lighting seems brighter in this shot than the other, or the depth of field changed and it shouldn't have. When you don't give the conscious mind something to do, it will fill its time with things you might rather it wouldn't do.

Production Design, Values

If your movie doesn't tell a story and isn't constantly titillating and tickling the audience's conscious mind with interesting imagery and sound, then they will read too deeply into everything they see on screen. They might see things that aren't really there and judge your movie based upon it. Films replicate three-dimensional space in a two-dimensional medium and sometimes the perspective can mislead. Unbeknownst to you the filmmaker, your set design and set decoration may be casting shadows that look like images the audience thinks is important to the movie. If they aren't intellectually and emotionally involved in the well-being and actions of the characters they will have to do something to fill the time between when the movie begins and ends and it might detract from the overall experience.

Sound/Music

A movie without a story that's filled with boring images and situations can be filled with music to keep the audience from complete boredom. Whenever there is a slow part you can just play a tune and people will probably stay in their seats until the song's over. A movie filled with songs is a lot like watching music videos for hours on end; it's fun but you could have done it for free on the Internet and been able to pick which videos you watch. So soon your plan of saving the movie with music will be met with critical ears who would have rather heard other songs. Some filmmakers might not use pop music but rather a score to engage people. The problem is that an audience uninvolved in the actions of the characters will have nothing better to do than pick apart the score and with it your film.

You don't have to include a story in your movie, but you do have to have something the audience wants to experience. Don't just expect to be able to make a film out of whatever images you think are cool along with situations that you've experienced in your life and have an audience sit through the whole thing engaged. If you include a story, you will be in partnership with the audience to make the movie experience better for all of us.