foxtrapper, you're right, they only wreak havoc in gardens, but they also open up a gateway for other predators (snakes).
Another valid reason to keep these overgrown rodents away is the damage caused by their tunneling under sheds and houses.
It results in foundation damage which can become catastrophic in heavy rains. Last summer I was close to loosing my garden shed and dispached another one that had been trying to start a tunnel under the house. un