I guess that is because particles in the accelerator are not alive, so you can accelerate anyway you want. Do you really want to round up a group of seniors and gives them different doses of alcohol and see how much you can accelerate their demise?
That's a strawman, a randomized control trial does not have to be dangerous. In fact, we already do randomized control trials, they are just expensive and uncommon.
An experiment is not required, as the behavior (acceleration towards demise) may be observed and tracked at scale in the field