For those still asking "WHY!?" this is happening the answer is pretty obvious. Tekken Revolution awhile ago did a character vote poll consisting of ten characters where the top voted one would be added into the game. The list had females, males, and even bizarre creatures like Tengu such as a giant mantis or a salmon. Unsurprisingly the result ended with Vampire girl being first place, Sexy Tekken Force Girl being second place, Shin Kamiya (fangirl #1 pick) got 3rd place, sexy zombie bride getting 4th place, etc. You get my point.
If a game like Tekken that doesn't make their fan-service aspect too obvious compared to DoA has a fanbase that would prioritize the "sexy" females over rugged males or bizarre creatures then you know how the overall DoA community would have handled it. Since TN is making the characters paid DLC unlike Tekken Revolution that made the female vampire free (with some big grinding involved though) that means whatever character they pick has to be marketable outside of a niche demographic and bring something different (even if minor) to the DoA table.
Normally, I would kind of agree with this, but plenty of the other choices were terribad. Let's take a look.
Elisa: A lot of people thought the storyline behind her was stupid. But, she was marketed on possibly bringing fireballs and other special attacks. That appealed to a lot of people. And there was much facepalming to be had when her big boob option was revealed.
Sexy TF Character: While the sexiness was played up by Namco personally, I saw a lot of people that voted her because it was a vehicle to possibly get a style like Krav Maga into the game.
Shin Kamiya: He clearly has his fans. People thought he could be expanded upon.
Zombie Bride: While female, she's also a zombie. Probably got votes on that alone.
Female Paul: Uh... Why?
Female Ganryu: Uh... Why?
Average, run-of-the-mill old man: wat?
Giant Praying Mantis: Plenty already think that Kuma, Roger, and Alex don't fit.
Salmon:
lolno. He was even marketed as not being able to do anything.
Tougou: He has his fans, but people kind of hate Lars and that probably ruined it for him.
It would be folly to solely extrapolate from who won "lol boobs are awesome" when there were clearly other things involved. And Namco was obviously pushing for TF lady pretty damn hard and that had nothing to do with the fanbase. But, probably all they
did take from it was "lol boobs are awesome." I wouldn't doubt it.