Why wasn't it backs, or hands, or the side of the cheek?
I think the sexual aspect was part of it, as sort of a "take back sexuality and make it less stigmatized" kind of thing. But in that case, why not the ass? That way it'd still be semi-sexual, but it would be equal-opportunity and a lot less sexual than breasts. That said, a lot of the personal-space and sexual-harassment issues would still arise with that, so it's still a flawed concept.

Because it wasn't as pure as it's being presented
I agree with you whole-heartedly.