If you dump a bunch of baseballs into a box you'll notice there's a lot of space left between the balls. Now shake the box and the balls tend to settle. Same concept applies with a dipper. What is happening here is that you increase the average density of the powder in the dipper by agitation. This results from the flakes/spheres/rods settling to increase the packing fraction.
Try tapping the dipper - the powder should settle leaving space for more.
Different powders will give different results depending on the particle's geometry.