Many people have complained about some of the things that go on during an NFL game, such as lack of replays and the PA announces not doing a very good job of getting the crowd hyped up and into the game. With the drop in attendance across the board over the past few seasons, the NFL has decided to pull back on those restrictions and promote a more "wild stadium".
"The at-home experience has gotten better and cheaper, while the in-stadium experience feels like it hasn't," said Eric Grubman, the NFL's executive vice president of ventures and business operations. "That's a trend that we've got to do something about." In hopes that professional football can mimic the wild stadium atmosphere typical of college football games, the NFL says it has "liberalized" its restraints on crowd noise. Stadiums will now be free to rile up crowds with video displays, and public-address announcers will no longer be restrained from inciting racket when the opposing offense faces a crucial third down.
I think in the Jaguars case, they do a fairly good job of this already at EverBank Field. The PA sets up the crowd well when the team is on defense, for the first down chant, and for the eventual "DUUUUUUVAAAAAALLLLLLL!"