It's also a popularity contest with the players sometimes. Votto is obviously beloved by his peers. Scott Lauber, in the Philly.com newsletter today, points out that with Herrera, maybe not so much (due to his long between-pitch AB habits, for instance). Of course those two players could be poster boys for the coded culture clash of "play the game the right way" and "it's a game, have fun."
Harper shouldn't be starting of course but he's a superstar and the game is in his home park, obviously those fans were motivated to vote more than any others too.