Because, let's face it, this is Torchwood, and all the good stuff happens off screen anyway.

Sad but true.

It's odd that Jack hasn't slept with Gwen. Clearly he finds Ianto more appealing, but he does find her somewhat appealing and he doesn't seem to place that much value on fidelity. And Ianto would probably take him back if he did cheat.

Then again, I don't think we've ever actually seen Jack cheat on Ianto. So maybe there are some morals hiding in his coat pocket after all.