My SWAG;
Tire cupping is impossible to completely eliminate. Tire cupping can be caused by a large number of issues and is to be expected on all tires, on all vehicles. The concerning factor is the degree of cupping. Tires are designed for 'load'/'speed'/'traction' but none of those variables take into account suspension, riding style, road, air pressure, etc...
Compound. A motorcycle tire (appropriate for our bikes) has variables compounds, it literally changes as you move across the width of the tire.
The center compound is hardest, the edge compound is softest. This is design meant to ensure that you get the highest mileage out of the tire but without compromising cornering grip. Note that the tread grooves span the multiple compounds of the tire. This means that all things being equal, those grooves are going to wear differently across their span based on where on the tire you ride (what compound), the air pressure in the tire, how you ride, etc.. Spending a lot of time under load on the edges of the tire is going to put more heat, deformation, and wear into that part of the grooves (starting at the leading edge of the groove which undergoes the most deformation). I suspect that the problem starts here. Tread grooves are a compromise between legal, performance, and aesthetic concerns. That compromise is where everything starts and together with actual tire design (compound) and manufacturing quality, probably come together as the single biggest factors in uneven wear.
The rest is mental mastirebation. (can you be more speculative than just a SWAG)
The second thing that happens is while you are riding is that you are moving the contact patch around the circumference of the tire. (the tire is rolling and the contact patch is hopefully in one place relative to the road). As the tire deforms it transfers the load into the rest of the tire, ideally this would be a perfectly uniform distribution... but its not. Tires can be perfect balanced but not perfectly true and even if they are balanced and true, that doesn't mean that they are perfect structures. Tires are built using an additive process out of non-uniform (imperfect) materials. While tires may appear to be round they are not and while the sidewalls have a rating, they may not be uniformly stiff (and are not) all the way around the circumference. All tires vibrate while driving - whether you notice it or not. This sets up both a natural frequency (based on being imperfectly balanced and imperfectly stiff around the circumference). Add to this the moving deformation of the contact patch and you have not just heat but also variations in forces across the circumference of the tire. This will contribute to non-uniform wear.
The byproduct of hard riding or even long steady-state riding is that you will begin to create wear patterns in the tire. In the case of the former (as
@Darbinco pointed out) is putting heat into the tire (as a byproduct of friction) which is going to cause those variable compounds to wear unevenly. During extended steady state riding sessions you may get some uneven wear just from the fact that the tire is imperfect and any variation in construction is going to set up a natural resonance in the tire which in turn could cause uneven wear.
On top of this, any suspension related problems (bearings, alignment, weight distribution, air pressure etc) are going to create their own issues, more often than not accelerating uneven wear.
Once the wear pattern starts (cupping is typically a pattern) it just accelerates slowly over time. It could be a case of some tires having the perfect storm of tread pattern, construction, compound that makes them worse than others for a particular bike (cup faster than others). I would suspect that all tire designers know this and some of them are biasing towards one target vehicle class, riding style, etc over others meaning that even given the same load class and tire wear that the target use case is different. A Goldwing vs 1600 GT as a loose example so some tires are just going to do better on some bikes.
/end of SWAG