Air compressor

Anyone know what typically fails on the compressors?
I pulled mine out today and started taking it apart as it wasn't working.
I see the piston is seized up. When taking the side of the case off, I was amazed at
how much crud fell out. What I can't tell is if there was supposed to be oil in this crank case.
I suppose it could be a oil-less compressor but then what was all this crud that came out?
Kind of reminded me of the crud you find in a set of carbs that have set for years..

They are oilless. They wear out because the bags on the shocks rupture, and they run until the piston freezes up in the cylinder. The dirt in the case is probably because the case may not be sealed for whatever reason, and dirty air gets into it. It can also be from wear and tear on the internal parts.

The compressor is similar to the cheap 12 volt compressors used for emergency flat inflation.