Why does the author use so many characters.

The novel's main story spans the years 1975 to 2000, but in a flashback reaches as far back as 1907 and beyond. In the style of hysterical realism, Smith cuts between incidents, points of view, and eras with movie-like deftness, weaving these disparate stories into one narrative. With such a huge time span involved, the at hour needs to utilize many characters to make the story work.

Would u mind provideing sum examples.