Why does Mrs. Pac-Man need a bow, lipstick, and eye makeup to show that she's a woman? Well, she's the female version of a male character, so she has to be somehow different, right? And how else can we signify femininity, if not with lipstick and bows and breasts? Anjin Anhut at How Not to Suck at Game Design explains why having the default character be a boy and anything girly-looking be a girl is a problem.
The dominant use of unequivocal gender signifiers on characters – therefore the reduction of those characters to not much more beyond their gender – is with female characters way more frequent and severely stronger than with male ones. Most of the time these signifiers limit the respective character either to the concept of femininity or to a sexual entity. There are also by far fewer female protagonist, which puts female characters at a severe disadvantage, when it comes to exposure.
In most groups, female characters just appear as one single member or as very very few members of that group. This is referred to as the “Smurfette principle”. It makes the gender of that female character a distinguishing factor, drawing special attention to the character’s gender or limiting the character to her gender.
The same goes for derivative characters. There are little to no instances where there is an original female character spawning a male one. On the other hand, on the subject of “distaff counterparts”, there are tons and tons of popular male characters spawning female counterparts.