I am not saying that flaps don't help. On the right aircraft they can help slow down the plane if it has a high wing loading. Try flying your plane at a safe altitude and deploy the flaps and slow to landing speed then retract them and see if the plane falls out of the sky. Then you will know how much they help. You don't mention how many people stall out a plane on approach with flaps deployed because of the additional drag the flaps create and if they have to go around how out of trim the plane will be with full power. I really believe the manufacturer test the aircraft before they are released and determine if it needs flaps or not. The Hangar 9 60 size P-51 didn't come with flaps because it doesn't need them while there P-51 1.50 size comes with flaps because it is bigger and heavier and can possibly help in some situations. I think most people like to have the look of flaps on there planes to make them look more scale and mentally think they are landing slower because they have the flaps down.
That is what makes this hobby so interesting because everybody has an opinion and can do what ever works for him. I fly mostly all warbirds and unless you go above the 60 size, I see no need to go to the extra work involved in putting in flaps. You also add weight with the extra one or two servos you use.
Good luck .