Why might authors use symbolism in their writing? ?

Allegory is a form in which the idea is everything. The author has composed the story according to a plan; the reader's job is to decode the plan. Characters in allegory are rarely more than figures standing for ideas. While allegory is rarely written today, many writers of academic/literary fiction use SYMBOLISM in much the same way - characters exist primarily to stand for an idea, and readers must decode the symbolic structure in order to receive the story. Allegory involves creating a fairly thoroughgoing pattern of SYMBOLISM in which all major events and characters in a story have a meaning beyond themselves and those meanings can be put together to make some sort of overall sense.