I play the opening myself, and I still ask that question. I found one kind of answer in a recent Chess Cafe book review by Steve Goldberg. He was writing about Timothy Taylor's new Pawn Sacrifice! (Everyman Chess, 2008)
Of course, in the Jerome Gambit White sacrifices more than a pawn, but often his two-pawns-for-a-piece material disadvantage is on the same level of loss.
Chapter 12, titled "Confusion," represents an interesting use of pawn sacrifices. Taylor explains, "Sometimes your opponent is just too smug. You look across the board, and there he is, wearing his Andy Warhol t-shirt, dreamily calm in the midst of his prepared variation/middlegame he’s crushed GMs with/grinding ending, and he just knows he’s going to win, and you’re just going to have to sit there and suffer, and he’s going to enjoy it."
Taylor’s advice is to "rip the gauzy comfort zone right off his smiling face! What do you do? You sacrifice a pawn for no other reason than to confuse your opponent! He says to himself, ‘That can’t be good!’ Then he thinks: ‘But why did he do it? – there must be some idea!’ Then, ‘I can refute this, but I have to leave my beloved comfort zone! Ohhhhh no!’"
Five games are presented in this chapter, and four of these "go from objectively lost, to confused, to winning." Fritz doesn’t approve any of these sacrifices, but Taylor states, "The confusion sacrifice is a very effective weapon against humans … The next time you have a bad position, or a position you simply don’t like, cheer yourself up! Sac a pawn just for confusion, then watch your opponent flounder! You will win many more games this way than if you drearily and unhappily defend."