You could break it down that easily. Fortunately, there is almost no technical development department today that does not work with 3D CAD. Architecture is currently still an exception, because in very many architecture offices 2D is still used for design and planning. Apart from that, 3D CAD data is usually available to visualize it with CGI. It is also no longer a problem to convert NURBS based surfaces and solid models from CAD to polygonal (tesselated) models. That means to make them usable for visualization software.
hen do you have to create 3D models by hand, i.e. model? Doesn't the CAD user also model?
Yes, he does, but very precisely, because he constructs models. These are absolutely true to size and contain a lot of meta information. (Information that is relevant for the creation of the component, the machine)
The 3D modelling we are talking about here comes from the film and games industry. Here we are dealing with "objects" of which there is no construction data. Plants, animals, humans, spaceships, etc. The software used for modelling does not claim to compete with the precision of CAD software. They are mostly organic objects and figures. The machines are fictitious and do not have to be built. So in which technical development areas does modelling have to be done? Architecture has already been mentioned. In the design and the draft phase you can fall back on technology.
CAD software can represent machine parts perfectly, but what it cannot do or can only do with great difficulty are organic shapes. For example, in automotive engineering almost everything can be designed in CAD, except for soft components such as seats. Only the rough foam moulds are designed. Upholstery, unevenness of leather and seams have to be modelled.
The same applies to furniture construction. There is also special CAD software for the production of soft hoses and electrical cables. But this often does not look very realistic on closer inspection. When machines or components interact with organic objects, modelling is essential. E.g. a tractor with a field and crops, a hair dryer with hair, a machine to produce felt materials with fibers. So whenever soft, organic things are needed, they have to be modeled.
There is one more special case, which we will not go into here, where 3D modelling is essential. Interactive applications for mobile devices or the Internet. CAD models are much too large for this application and cannot be processed by mobile devices. They must be simplified and re-modelled.