Good question. Here is another one: do you think most women would have sex with someone they met a few days ago and comply to every fantasy asked, to the point of having a threesome with someone they hate each other guts - like the characters in this game do? I ask you because you seem in need to be reminded this is a game filled with characters, not real people in line with reality.
Man, the whole point of drawn (or 3D designed) art is that it can say "fuck you" to wathever the artist and its audience find unappealing into reality. So the question is not "What do you think tits that size look like?" but "If you can draw them the way you want them to look, why would you draw them saggy?". Look at how Oni drew Emma's a few years before Storm: her tits are at least as big as Storm's, but shapely, no boner-killers.
If you can't get this, I think you're simply not built for mainstream porn (and imaginary art, be it porn or not).