The use of curbs and gutters protects the edge of the asphalt from damage due to vehicle loads. Vehicles driving and/or parking to close to the edge of an asphalt driveway will cause the edges to buckle under the weight.
The curb holds the asphalt pavement in place, even if a vehicle drives or parks on the edge of the asphalt surface. Secondarily, the gutter and/or curb define the surface of the driveway and as a general statement individuals will not drive as close to the edge of a driveway that has a curb. In areas that are subjected to snowfall, curbs define a clear snow removal area, preventing damage to adjoining landscaping. Landscaping on both sides of a driveway with curbs is better defined. Grass can be easily trimmed, mulch and other landscape fill materials will not end up on driveway surfaces. Driveway lighting is somewhat protected from potential vehicle damage when placed on the landscape side of the curb, as the curb offers a physical barrier.
By adding a curb and/or gutter you will increase the ability for proper compaction of both the foundation and the surface layer of asphalt. You will be providing better drainage for the parking lot and driveway. You will lessen possible damage to edges by vehicles.
Add curb appeal. A driveway with curbs is cleaner and neater than a driveway which has no defining elements. This feature alone, makes a driveway with curbs much more visually appealing.