A monument isn't just a large piece of rock or bronze. Size does not make a monument, meaning does. One must be a great believer in meaning, and ask what things mean. An epic isn't just made of a great number of words, the theme is what makes it epic, or monumental.
The ancient world only dealt with kings and other royalty as fit subjects for representation. The common people are shown doing their common things, but it was kings, great kings and queens who made the life and livelihood of the common people possible, and so they were revered and honored because their task was monumental.