I think it's part of gamer developer/marketer culture - they both overlap right in the area of crotch motivation. Game developers are pretty much enslaved, so they don't get the essential social / life interactions, including romantic development, that is essential to us humans. While marketing has a very high population of brains-between-their-legs BS artists (let's face it, it's the perfect vocation for that type, so it's no surprise they gravitate to it) who can actually prove that pushing the sex button results in higher sales of pretty much anything.
Put the two together regarding character design and even in franchises where appearance is already preset and the audiences' expectations are well defined, you get Hulk Batman and Sleazy Quinn. Given a blank canvas, you're going to get ridiculousness out of that combination every time.
I do recall that the creators of Fallen Earth once fought that stereotype by having plain-featured women. From what I saw, the face generation devolved that into mild ugliness, and after fans made enough mention of it, they tweaked it so the women looked considerably "cuter". Now that I think about it, I don't recall any other MMO where your character looked pretty much ordinary, and it didn't bother me a bit as far as identifying with my char. In fact, it was kind of all right to see a bunch of ordinary-looking characters (for a post-apocalyptic wasteland setting, that is) running around.