Stump Grindings make great mulch!
Stump grindings are left behind because they fill the hole from where the stump was ground out. It is much more effecient to do this because it would cost the homeowner twice as much to have the grindings removed and then fill it in with soil purchased from a retailer. In addition, the grindings are nutrient rich and over time, mix with the soil, decompose and settle down into the earth again.