Heimerdinger Item passage.

I would like to discus how the items in the game do not seem to work on Heimerdinger's Cannons. This is not a real serious point, i would like to know why the item's ability do not affect Heimerdinger's Cannon. Best Example: Liandry's torment 2nd passive the burning section, <--- this passive does not go about affecting the turrets to inflict the passive to the enemy at all. Spell vamp is also another passive that can not be used with Heimerdinger's cannons.