Why is the visual fidelity of some things affected by Effects Quality and not Character Quality?

Example pictures from the post:

Visual quality of tower being affected by the Effects Quality:

Very Low Effects - http://puu.sh/gMsNO.png Very High Effects - http://puu.sh/gMsOv.png

Champions are also affected:

Volibears entire model - http://puu.sh/gMuFH.png Kog when he uses his W - http://puu.sh/gMwDH.png Hec when you get max stacks on Q - http://puu.sh/gMvZ6.png