It could be artists or audiences. It really depends on artists. Some artists are more comfortable letting audience make decisions, and others have concrete meanings that cannot be changed by anyone else. Unfortunately, even if artists explain the concrete meanings to the audience, some audience still may interpret the way they want to.
Robert Adams has strong feelings about nature and express it through his work, but he also knows viewers do not always share the same interpretation. Iñigo Manglano-Ovalle also mentions that his art has underlying politics, but in his case, he does not want to tell viewers his political position. His intension is to have his art work as a platform to start debates among viewers.
When I create my own work, I try my best to guide viewers to the main messages since my work comes from specific concepts. I do not want to tell viewers exactly what to feel, at the same time, I cannot leave the meaning as whatever viewers feel like.