We agree, why would a lesbian relationship involve a man, even if one of the women is bisexual? Basically, the Janet/Wanda lesbian relationship, I'm not interested in involving a man even in the future. But even if it did happen, why would we need a strange guy next to the two women? Why not someone we already know from the game?
Well, because there's already will be a hell of a lot of pure lesbian relationships with Nicole, Lois or Faye in this game and you need to add variety to the picture to keep your subscribers entertained and Janet with her secret sexual relationship with Steve is a perfect characters to seduce Wanda into a threesome sex. That's why.
Plus, in my opinion, Janet is a whore who is looking for new sensations from life and for her Wanda will only be an object that will bring new temporary pleasures into her bland life and adding a man to their relationship for her would be like pouring gasoline directly onto a fire. There will be no happy ending for Wanda in this relationships. Just as there will be no romance or happy ending in her relationships with Terrance who will use her and throws her away after some time leaving her with a broken psyche.
I think that the overall plot of this game is designed in such a way that Wanda will only become truly happy in a relationships with characters like: Nicole, Gene, Faye, Lois and
maybe Harry. Characters who really love her.
All other paths/relationships are Wanda's tragedy and one of those
possible bad endings that scriptwriter himself mentioned if i'm right.