Oscar Wilde is quoted as saying that, "All art is quite useless." If so, how does that explain the value of art? The mistake is to link the idea of utility with the idea of value. They are independent concepts.
Space is the complement of shape. Change in use of space affects our perception of shapes (and the reverse is also true).
Another essential element of art is a shape, which is a 2-dimensional area within a space.
A line is one of the basic elements of art. The most obvious is a directly visible solid path. But, consideration of implied lines is more interesting.