S03Ep12 The Psychic Vortex

Just watched the episode where Penny and Leonard fight over Psychics. In that Episode Raj and Sheldon Go on to a mixer at the college, and meet a couple of young ladies.

I know later down the road we have Amy coming in, but why didn't these two ladies become a love interest for either Raj or Sheldon?

I mean it was pretty clear that the were kind of a package deal, but the one into Sheldon I think would have been great for both to be in a relationship.