It depends on the type of plane and its wing loading. You do not need flaps to land a light acrobatic or 3D plane. On a heavy warbird, flaps make landing so much smoother and decrease the chance of nosing over or bending the retracts, especially on a grass runway. Flaps provide additional lift (and drag) on landing, so you can bring a heavy plane in at a crawling pace and gently set it down onto the runway. Landing a plane with flaps is different than landing a plane without flaps. You do not want to do a long shallow approach with the flaps deployed.