Yeah, it is a common misconception. There are software packages that can take the scanned data and create a non-parametric 3D CAD models of fairly simple geometries, but they are very expensive, require a very clean scan, and still only produce a model that is difficult to manipulate any further. The industry is getting better, but there is still a long way to go. I have been playing with 3D scanners for about the past 10 years at various jobs. Normally get a phone call once or twice a year from a sales rep for Keyence, Faro, or someone else promising me that their latest gadget is the greatest thing since sliced bread, I will have 3D CAD models in 2 minutes, blah, blah, blah. I invite them in for a demo, and typically I set a compressor housing off a turbo on the table and ask them to generate a model of the involute volume. Of course they can't because the scanners require line-of-sight and I would have to section the housing along multiple planes, take multiple scans of each section, stitch the scans together, and then import the scan geometry into CAD and use it as a guide to build a proper parametric CAD model. If the rep gets snotty, I ask them to scan the DT-466 display model we have in the lobby. "Well you have to disassemble it first..." In the end, the 6 figure price tag just doesn't justify the results. They are good for resolving simple external geometries, mounting faces, and hole patterns. Complex castings and assemblies, the technology just isn't there yet.
