No.186
Is Helen not framed as a stand in for beauty, that is Aphrodite herself? A sort of avatar for desire. It's not just some cultural archetyping, I think this goes back to the basis of what is foundational to Greek metaphysics (the mere sensing and being we find in Parmenides and also in Aristotle) and probably Indo-European myth and metaphor.
Desire always moves on, it never stays, and Those-Who-Desire would follow it anywhere. That's probably the core of the tale. The collaborative nature which designed the Illias and Odyssey shouldn't be neglected there. The Illias and Odyssey were compiled to be different works. In a narrative sense a coupling in the most literal sense of one with the other would fail. What is desired is desired because of those who desire, what is lost is trying to be found. These tales are ancient and at the very root of Indo-European tales. It's probably that simple, while trying to deliver good entertainment by bards stitching hexameters together to make these tales.
To answer your question, and from what I think you're pretty close to the answer yourself, though Penelope would've stayed with Menelaos, he would have left, and Odysseus would not have journeyed home for Helen, for the desire or lust for beauty. He journeys home - for his home. The very grammar of our language has retained this.