Buildings 3D models are often blocky because they use low polygon (poly) counts or simplified geometry to balance performance with creation and loading speed.
This simplification is critical for real-time apps like games, AR/VR, or city mapping—high detail would slow rendering or bloat files, making them unrunnable on most devices.
To reduce blockiness, increase the poly count in tools like Blender or add texture details (e.g., brick patterns, window decals) to mimic complexity without extra polygons.