Why are the wicked joyous?

St. Ambrose had a very good answer to this question.

Perhaps you say, Why are the wicked joyous? why do they live in luxury? why do they not toil with me? It is because they who have not put down their names to strive for the crown are not bound to undergo the labors of the contest. They who have not gone down into the race-course do not anoint themselves with oil nor get covered with dust. For those whom glory awaits trouble is at hand. The perfumed spectators are wont to look on, not to join in the struggle, nor to endure the sun, the heat, the dust, and the showers. ...

As Tom points out, this turns the whole "gospel of prosperity" on its head. We are working for the bigger reward than ease in this life. Its nice if it comes along, but that's not the point at all. It is about our immortal souls.