I will venture a guess at this one. It probably isn't a full answer, and may not be the right answer. But it is something to consider, and maybe someone will correct me. Drag/drop into Lightroom would imply that you would start editing the image directly. But Lightroom doesn't make changes to the image. Images must be added to a catalog. Yes, even that cloud version utilizes a catalog. The user doesn't have direct access to the catalog like Lightroom Classic users do, but the catalog IS there, and images are added to the catalog and that is where the adjustments are stored. That is what the "Add" process is all about, keeping images properly organized within the Lightroom system.