Why do writers use symbols in their work?

Authors often use symbolism to communicate a deeper idea than they actually write. Symbolism is an object used by an author to open doors of meaning. They use objects, actions, and characters to give more meaning to the thing itself. In literature, characters can symbolize something of a deeper meaning. Symbolism helps readers connect the story to other main ideas.

Is "ancient times" in your question a story, or do you mean actual ancient Greece?