Fundamentally, to me, cheating says in bold capitals "you don't get equal rights to me".
If they wanted their partner to get equal rights, they'd offer an open relationship (and if the partner wasn't amenable to it), they'd end the relationship, and let their partner find a monogamous partner.
They don't.
They apply different rules to their partner than to them, they act like they have special rights and privileges that their partner doesn't have.
You also don't want to cause pain and I stability to someone you truly love.
And those are almost certain for victims of cheating.
True love would include empathy. Cheating included no empathy.
I suppose cheaters lack empathy (as well as integrity) and that's why their love can never get a true/real/fair love.