Blocks doesnt keep the "CanPlaceOn" Tag after being Placed but they keep names and such...

The Shulker Box could be really usefull as a backpack in adventure maps.

but you can place them only once...

I know its maybe abit like a suggestion... but if the shulker box keeps the name... maybe its a glitch if it doesnt keep the tag! I dont know! but to be honest it doesnt really metters because its a thing that should be changed/fixed