When and why would you use datum targets instead of full datum features?

Datum targets are used when a full datum feature surface is too large, impractical, or unreliable for datum establishment. Applications include: rough cast/forged surfaces where only specific points are machined, flexible parts that need specific contact points, large surfaces prone to warpage, and parts where only certain areas are functionally significant. Datum targets can be points, lines, or areas, specified with target symbols indicating location and size.