Why does the author include the information about New York and Los Angeles?

New York and Los Angeles are the top two cities for casting actors.

Most movies are filmed in New York and Los Angeles.

Most commercials are filmed in New York and Los Angeles.

New York and Los Angeles have more agents than any other cities in the United States.

The author includes the information about New York and Los Angeles to highlight the significance and dominance of these two cities in the entertainment industry. The information about them being the top cities for casting actors, the primary locations for movie and commercial filming, and having a higher number of agents than any other cities emphasizes their importance and attractiveness to actors looking for opportunities in the industry.