Why, therefore, is hold baggage submitted in the normal manner at the check-in desk not verified in this manner, apart from the anodyne "did you pack this yourself has it always been with you"
Firstly, The number of customers that choose to pack Lithium Batteries in their checked baggage is very, very small - let's face it, not that many people carry spare batteries - most batteries are attached to the device that they operate and people are reluctant to check such items in (not least because they wish to use them in-flight). In terms of volume, the threat is low - until you move cabin baggage to the hold that is.