
Basically it is to hold the dogs interest especially if they are shown freestanding, otherwise with many breeds they will ahve their noses on the floor :D
If you have a stacked breed that isn't large they are generally not baited as they are held in place.
Some breeds are stacked and baited, I suppose because if your qare holding a big dog in place it could move away out of your grasp more esily without bait????
If I didn't take bait in the ring then I would have the dogs with noses glued to floor and no chance of them moving with ehad up let alone standing.