Photograph by Richard Termine/PBS.org.On the surface, there is nothing pernicious about the news that HBO will begin providing financial backing for five seasons of Sesame Street, which would air on the premium cable network nine months before reaching PBS viewers. As Emily Steel explained in the New York Times, the nonprofit Sesame Workshop has struggled to keep up a robust production schedule for the long-running children’s educational program, largely due to declining revenues from licensing and DVD sales. What’s more, PBS only accounts for about one-third of Sesame Street’s viewership—most kids stream the show and would be unaffected by HBO’s involvement, which would bring in enough money to produce twice as many new episodes per season and spin off new programming.Jessica Winter is Slate’s features editor. In practical terms, this is good news all around. In symbolic and historical terms, however, it’s terribly sad. To understand why, we just need a bit of history.