Ilikeyourbeard got it one.
Odd thing is I posted on that hours ago. 
If you put bi women in, surely the only women they could actually pair up with would be other bi women? I am sure there are not many women who would be happy to pair with a women, unless they have considered it before.
And then I am sure some fame hunger people would enter a gay coupling just for the shock factor. Not nice for the Bi women.
Nor is it nice to put them in there to make their sexuality an issue for publicity.