Gable, sump pumps are necessary in houses where the foundation intrudes on the water table in the ground. Beecause your foundation is below the average or perhaps high water table, the builders gave you a sump pit to pump water out. If they hadn't, hydrostatic pressure would eventually build to a point where your foundation would leak water and damage the structural integrity of the home.
Because you say that the pump is running constantly, I would guess that you are currently experiencing high water levels in your area (snow melt or high precipitation are likely culprits). Regardless, you do need that sump pump to keep your basement dry. Regards!