In nature it’s random. As you point out, you could probably also force it. But that would be a little self-defeating here since one of the objectives was to determine the half-life. imo
I think you are assuming that matter when left alone by us is “natural”...but matter is always interacting with other forces so it is never truly in a pristine unaffected state....the implication of altering the decay rate could be that we can speed up dangerous radioactive decay in a controlled environment and therefore render safe, formerly radioactive waste..