Art is a personal expression of how we see the world. Indeed one of the first things that new artists are taught is to truly "look" at the world and see what is actually there, not what we imagined to be there.
So in that case why isn't everyone's art the same, it is after all often meant to be a representation of reality? The answer lies in the complexity of both the artist and the viewer's mind and their perception of that reality.
Just as beauty is in the eye of the beholder, art is only art if the perceiver believes it represents an emotional or significantly valued impact on the senses. To make that impact an artist can play with reality to bring out feelings and impressions that stir the passions and reshape how the viewer sees the world.
Art ultimately is like beauty, a concept that is completely personal to each of us.
Art can stir emotion.