CAM users need the ability to create construction surface geometry in the assembly environment.
Editing the part to add it isn't viable due to it messing up drawings or isn't possible because the file has been released and locked.
Creating an additional file to create the surface geometry makes a mockery of using an integrated CAM solution inside Inventor.
CAM users often need to patch holes / pockets / slots to simplify toolpaths and give the user more specific control over toolpath behaviour. This is standard practice in the CAM world and Inventor currently doesn't allow that to happen in the Assembly environment (the best place to do CAM).
Both Fusion 360 and Solidworks make this possible, but Inventor HSM users are held back.
