I think the difference in Celebrity Jeopardy and other shows that have celebrity specials, versus DWTS, is that Jeopardy is a show for regular people to win money. So, when they have the celebs on, they want to make a point that the celebs already have enough money and are doing the show for fun and charity.
DWTS is a show like any other on TV in which professional "stars," <cough!> actors, entertainers and celebrities are hired to entertain us. They are paid a salary just as they normally would be for any other show on TV.
Makes sense.
I guess I was comparing it to a show we have here (Canada) called "Battle of the Blades" which is sort of like like DWTS but on ice. The pairs are hockey players (NHL mainly, but also Olympic/World team members who weren't in the NHL) paired with a figure skater (many Olympians and World Champions). They are all playing for charity.