There are several reasons. Players in general like characters to be at least somewhat familar. Sure, designers and consept artists could go ahead and create volumetric fog based chaotical shaped blob but that character would come right back bumerang style from animators and programmers. They certainly ain't going to spend huge amounts of time to create complite separate animations, shaders, collision detection ect ect for one strange looking alien. Xbox360 was already in huge problems with normal Mass Effect characters.
Quote from Bioware's Patrick Weekes
"In addition to time constraints, a female version of an alien species is another unique memory asset for an area. So in a place like one memory chunk of the Presidium, for example, you might have:
- Male human
- Female human
- Male turian
- Male salarian
- Asari
- Hanar
That's cutting things close, even with the asari using the same skeleton as humans. If you wanted to have female turians, you'd have to cut something else out of that area in order to make room for it. So the area with female turians doesn't have male salarians, for example.
Nobody on the dev team is in love with having a universe with a bunch of the alien women off behind a wall like Vera on Cheers, but that's what we've got to work with, for tech and time reasons."
It's alright to be critical on graphics and art direction but in the end you have to work with certain game engine and know the limits of some closed system like Xbox 360. Thane is good model because designers and artists know Unreal engine 3 limits and try to do the best they can with resources and time they have. Facial expressions are really hard and time consuming to do and this "next" generation have not done good job in 'em. I hope animators get resources (time and good design tools) they need for 'em in the near future.
Sounds like the 360's age is already showing. So what bio is telling us is that they can't render a bunch of different aliens (genders) on screen because the POS360 lacks the memory or whatever.
This is why the PC still is the best platform for playing and to develop for. Why doesn't the PC gets any major lobbying?
Oh I see.... MS and Sony wouldn't like that. Bastards.