Why is displacement 3D model so missing?

Displacement 3D models are less common because they require more computational resources and complex workflows than basic or normal-mapped alternatives. Displacement physically alters mesh geometry (not just faking detail with textures), increasing file sizes and hardware demands—making it impractical for real-time uses like games or apps. Normal maps, which mimic detail using surface textures, are far more efficient and preferred for most projects. For high detail, use normal maps for real-time work first; reserve displacement for offline renders (e.g., movies) where resources aren’t as constrained.