I would guesst aht the added value of RAL is being a formal standard, such that it can be mandated by laws and regulations to paint things with a given RAL color.

For example, refurbishing a building within a protected area (close to a historic monument is a typical scenario) will require the use of materials (paints, window frames, doors, blinds) coated with a specific subset of RAL colors, selected by a public body to match the intended scenery.