I completely agree that for simple things like a panel with a slight sag, there’s no reason to simulate for visual purposes. Also I expect that the finer wrinkles and creases in the fabric in the first images posted are just a good texture or bump map.
For more complex folded fabrics though, I think I’d struggle to make it look realistic just modelling manually.
Anyway, here’s another example with some draping over solid objects.
drape_over.gh (52.1 KB)
One issue I was sometimes finding with this type of simulation when just using collision between the mesh vertices and the solids was that around sharp edges the fabric would tend to cut through the corners.
In this definition I added a new scripted goal to do collision between the solids and the lines of the mesh edges, which seems to improve this. For that scripted component the first time you open the definition you’ll need to set the referenced assembly location for the KangarooSolver dll, which is usually in C:\Program Files\Rhino 6\Plug-ins\Grasshopper\Components