Honestly i don't have a problem with boobs that are a little too big, but the problem is games stick to one type only, variety matters in body types.
Look at it this way, everyone expects milf's to have an exaggerated busty body, lets take the pornstar Brandi Love as an example of the Milf/Glamazon build, she looks great but that doesn't mean that less busty milfs aren't great as well, like India summer
example 1 Brandi Love and India summer
the same happens with all the other tropes, naive schoolgirl/little sister well that's gonna be Riley Ried, but for a twist we'll bolt on some over sized boobs, perhaps.
the same way when they go for a busty character around the same age as the MC they'll go for a Mila Azul or Jessa rhodes type body rather than Siri
Example set 2, "Busty"
Now in part this is due to people being able to play to their preferences when making characters in daz an people like flat or huge, the downside is that people like me who like a little balance, you know the B-D range don't get very much of that. now i'm biased, i'm all for the happy medium in terms of boobs and ass, too big can look ridiculous, too small can look childlike and i'm not a fan of either of those.
Now in part this is due to Daz, since that is the standard software used these days. The problem is that Daz content creators have no reason to make normal people, the Daz flagship model Vicky (8 at the moment) is almost 6 feet tall, that makes her a runway model in terms of height, in fact most of the Daz main women are over 5'8 with certain exceptions like the asian girls who sit around 5'3 to 5'6 which is far more realistic, this means that most clothes are set for women around this height, as are poses and scenery, for compatibility sake as devs are passively encouraged to stay around this scale.
Now consider proportions, Brandi love is around 5'8 and she has a 34DD/E set of boobs, they don't look too oversized on her IMO just big and busty, you certainly can find far more ridiculous sets of boobs in porn. The point is the taller the women the bigger the boobs you'll need to make her look busty and as such this encourages Dev's to inflate the chests of their girls, effectively raising the average from the C range to the D range, now you want you're girl to look above average, well that pushes her to the DD range, you see where this is going?
This means that some seriously beautiful women with bodies like, for example Malena Morgan, Mia Malkova, The Red Fox(Michelle), Nia Nacci and Leah Gotti simply won't be seen in games.
Example 3, the happy medium
TL: DR blame the combination of: Daz model scale being unrealistically tall, making larger boobs required for the same "look" to be achieved, Porn/viewers wanting either busty or flat depending on preference and being less invested in medium breasts since they are more difficult to fit in a particular niche/fetish and are considered "ordinary".
Yes of course using pornstar bodies as examples in and of itself could be considered ridiculous, however that is what erotic games are building on at least to a degree.
People want fantasy, however fantasy without reality becomes empty quickly.
