Rapid development is the benefit of the old-style gambits. An opening such as 1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 (known as the Danish Gambit) is virtually never played nowadays, but White does get good value for his pawn(s). Some trainers recommend young players try this out to learn how to get the best out of rapid development.