Because smart home wiring — CAT6 for network and access points, speaker wire for in-ceiling audio, HDMI conduit at TV walls, power for shade motors, neutral wires for RadioRA 3 lighting control — must be installed before drywall. After walls are closed, adding any of these requires cutting drywall, fishing wire through wall cavities, patching, retexturing, and repainting every surface the wire crosses. Rough-in costs during new construction: $80–$150 per CAT6 drop, $60–$120 per speaker wire run. Retrofit costs after drywall: $400–$900 per CAT6 drop, $350–$700 per speaker wire run. The economic case for smart home planning during construction is clear — and the consequences of not planning are permanent. Once the wall closes without the right wire, the choice is an expensive retrofit or a system that doesn’t include that location.