Grinding a stump is fast, contained and leaves the surrounding lawn and any buried services alone — the grinder works down through the stump itself rather than excavating around it. Most jobs are done within a couple of hours and the area’s usable again the same day.
Digging a stump out, roots and all, is a different job entirely — a much bigger excavation, more disruption to anything nearby, and real risk on an older Ōmokoroa section where buried pipes or cables aren’t always exactly where the plans say they are.
The only reason to dig rather than grind is wanting every trace of root gone — typically because a new garden bed or lawn is going in on that exact spot and any regrowth from a live root would be a problem later.
For clearing a spot, levelling for a path, or just getting an eyesore gone, grinding does the job with a fraction of the disruption.