Goood Question !
I think the reasons are twofold.
On one hand, there is this college in Utah that trains specialized PAs as 'radiology PA'. I believe that many of the students who graduated from this program where RTs before. But the development of their curriculum and the development of their scope of practice is outside of the sphere of influence of the ACR. While the emphasis of this RPA business is on interventional and procedures, there is nothing in the books that keeps them from interpreting a limited scope of studies.
On the other hand, the ARRT, the organization of radiology techs was pushing to get a path of advancement for their constituents, essentially with or without organized radiologies support. ACR made their support of ARRTs push for the RA programs contingent on the specific exclusion of interpretation from their scope of practice (at least for now).
So, one could say that the decision to pick up that stone is a bit motivated by the fact that there are two other people already standing there willing to drop something on your foot.
Also, by dropping the stone yourself, you can try to aim in a way that it just crushes 2-3 minor toes rather than a substancial parts of your weight bearing apparatus