User blog comment:Nabukad/A question: Why so sexually attractive females?/@comment-3974211-20131002205358

Large breasts where how female champions were originally identifiable as female - back when models were really low-rez (and frankly poor). You have champions like Janna and Soraka, who were very curvy and showed off a lot of skin (without actually being topless) - but those were immediately identifiable female traits. Kayle was actually believed to be a guy be a large portion of the community until her visual remake.

To be honest - except for maybe Sona, Janna, Evelynn and LeBlanc -think all most of the females have appropriate proportions and/or outfits for their characters (and Evelynn is original-40).