People who add you to flame you after a game .

Why ? Just why ?

I don't get it really. It's not rare that when there is a flamer/toxic etc.. that i ask them to stop or tell them they're wrong etc.. Sometimes i'm telling them that what they just did was wrong (most common example:Vayne going to deep and flaming her team after being destroyed ,i know you know what i'm talking about here..) And as a result,this person wants to add me for obviously flaming me i guess. I never accept them but i just..don't get it.

Why ?What's the point ?