So, what am I missing?

[Neale]

If you take a look around, there are a number of sample files of test objects (thingiverse.com is a good place to look). Classic starting objects are simple cubes around 25mm on a side which are useful for checking print quality, calibration, etc. I agree that cardboard isn't a good surface for testing as it is unlikely to be flat enough - if you are aiming at getting the first layer extruded with the nozzle at half layer height above the bed, which is a good starting point, then that's pretty demanding on flatness.

They are indeed fascinating things to watch!