@LARGames Plenty of answers.
1) In our world we tend to like bigger, and yet there's fewer of them, no? Could be a paralelism, though I doubt the author went there.
2) Maybe small are prefered PRECISELY because they're rarer.
3) To create a situation where the MC has to "console" big breasted girls. Personally I find it refreshing, it's normally the other way around.
@LARGames What I meant is refreshing is the big tiddy neesans being the ones that need to be consoled cause they're underappreciated. Normally it's the flat chests that have esteem issues.
I don't disagree that it's more of the "MC likes big boobs", but I mean... I'd say most men prefer bigger tiddies. It's genetic.
Therefore, the author prolly prefers big tiddies too, and therefore he creates a world where the MC has big tiddy girls. It's pretty reasonable, imo.
@LARGames Not really. There's studies about it.
Wide "womanly" hips suggest an easier time at childbearing and childbirth. The whole "thiccccccccccc" thing is not just a meme.
Ample bossom (aka, big boobs) suggest an easier time producing milk and an easier time feeding the baby.
Genetically, instinctively, it's what males look for. A female that will deliver his seed.
And after that, cause we're people and not animals, you add the rest of the stuff. Sure, culturally we can push one thing or another (like super thin supermodels). Personally you can like small boobs, or glasses, or whatever. But originally? Yeah, it's genetic.