Why a perfect 3D scan still isn't "a BIM model" until someone actually models it.
A team laser-scans an existing building, gets back a gorgeous, dimensionally accurate 3D point cloud, and someone on the project says "great, now we have a BIM model of it." That sentence is doing a lot of quiet, incorrect work. A point cloud is real, extremely accurate spatial data — it just isn't a BIM model, and it never automatically becomes one. Getting from one to the other is an actual modeling task, usually called Scan-to-BIM, and skipping that step is one of the most common — and most expensive — planning mistakes on renovation and existing-conditions projects.