Basically, in response to the question regarding Kim, "Why pointy?" the creators actually originally planned for Kim to be complete flat, as opposed to pointy, but the censors wouldn't allow them to do that. This was to contrast her with her in-school rival Bonnie, who was designed to be the most buxom.
In light of this censorship, they didn't want to simply give Kim boobs that were smaller, because it's just in the nature of animation to go slightly off model here and there, and there would inevitably be frames, inbetweens, and whole segments and what not where her bust would be a different size than what they wanted. They decided to make her pointy to get around that issue and to convey to the audience that she's more modestly endowed than the rest of the female cast.