Why do my ears pop if the cabin is pressurized? Simple question:

If a commercial airline cabin is pressurized, why do my ears pop as we ascend and descend? I was always told this was due to a change in pressure, but if the cabin and my body are at the same pressure, there should be no force causing my ears to pop.
Here is an illustration of how cabin pressure changes during a typical commercial flight:
image source: http://aerosavvy.com/aircraft-pressurization/

Note how when the pressure outside the aircraft is changing, the pressure inside the aircraft is also changing, but not as much.

During the flight shown here, you would experience about the same pressure changes that you would in an unpressurized Piper Cub that only went to 7000 feet.