I have to agree with Capriracer that “irregular wear” is a better term. “Cupping” is sort of a nebulous term that is often used to cover any of a number of wear irregularities. Irregular wear can be caused by bad shocks, bad suspension components (tie rod ends, ball joints, or whatever), and even a defective or improperly balanced tire. Or a combination of problems.
The only really clear irregular wear is feathering caused by bad toe-in, smooth center wear (overinflation), and excessive edge wear (underinflation…or habitually speedy cornering).
I also believe that once irregular wear becomes obvious it has already established a wear pattern and unless the tire tread is skimmed on a special tread-cutting machine it’ll never wear normally.
I agree that irregular wear is a symptom, not a cause.