Real cause of "rivering" or cupping? Air pressure?

Here is a reference to tire wear issues and some of the causes. If you scroll down to Erosion wear, you will see a perfect example of rivering. clicky. We had an 01 Ambassador, G670 Good Years and Aligned by a good truck shop before tires installed and aligned again in 10k miles and both fronts looked like this at 15K.Rotated them to the back and figured I could get 3 rotations before replacement by age. Hope this may help, Happy Trails Bert