Cute and attractive share a grey fuzzy line. It’s also well understood that sex sells. We also know that humans tend to feel more positively towards attractive (not exclusively sexually attractive) people/things. So it would make sense to make a product attractive, and, if anthropomorphic, with generic attractive proportions.

If kids find it cute and appealing, they are more likely to ask to see it. If parents see it’s cute, it feels more child friendly, and even though they may not find it sexually appealing, good proportions are still easier on the eyes than disfigured or grotesque (plus it can be more relatable). Then you also have the adults who find it sexually attractive, and as stated previously, sex sells. You hit a much wider audience using generic attractive features and cutsy-ness, than singularly one or the other.

This is in no way iron clad fact so much as personal musings on the why. If the Bunny was not seen nearly as attractive as the current design, would it garner so much attention, and therefore free advertising?