We had this debate back last summer. Our new rule was a compromise out of that and I really don't want to change things so soon again.
Additionally, positioning a flat part on a flat surface is easy in all the major editors. Positioning a curved part on a curved surface is non-trivial. Therefore there's a good case to be made for allowing the latter and not the former. If and when we adopt a part snapping standard and it is implemented in all major editors (currently LDCad and LeoCAD) we can revisit disallowing the rest of the sticker shortcuts.
Additionally, positioning a flat part on a flat surface is easy in all the major editors. Positioning a curved part on a curved surface is non-trivial. Therefore there's a good case to be made for allowing the latter and not the former. If and when we adopt a part snapping standard and it is implemented in all major editors (currently LDCad and LeoCAD) we can revisit disallowing the rest of the sticker shortcuts.