This is because most theatre organizations in the United States do not put on many Greek or Roman tragedies/comedies. This is true because of social publicity. Even non-theatre-goers have heard of Broadway and/or musicals that have been taken to film such as Les Miserables, Sweeney Todd (which Stephen also wrote), Mama Mia, The Phantom of the Opera, and Rent just to name a few.
Another show influenced by earlier playwrights is "West Side Story." Upon a closer inspection, the popular musical, one would begin to realize that the production is actually an operatic form of Shakespeare's Romeo and Juliet. The two houses that are "both alike in dignity" are (in West Side) actually two opposing street gangs known as the Sharks and the Jets. As previously stated, non-theatre-goers were influenced to this modern adaptation of Romeo and Juliet by way of film. Besides actual Shakespearean actors, it can be argued that Stephen Sondheim is one of the main driving forces that maintains the integrity of Shakespeare's works and keeps them modern and mainstream; and in some instancesactually improve them. Romeo and Juliet is a love story that expresses how powerful love can actually be. However, West Side Story exclaims all of this and more. West Side has served as a driving force since back in the late 1950's against gang violence. West Side Story as a tale of love across the divide of two street gangs, one Latin and one white-ethnic controversial show in which Act I would end with two principal characters dead as a result of gang violence (History.com). Of course, this show was set to be a hit. With lyrics by an innovative new composer and a story concept pulled directly from Shakespearewhat could go wrong?.
No doubt, Sondheim was a Shakespearean fan and a follower of his philosophies; so much so that throughout his career he has developed a process of using his musical creativity to revive previous works of Shakespeare, Roman, and even Greeks.