User blog comment:General MGD 109/Demonic Omens/@comment-5619706-20130216043309/@comment-5619706-20130216043801

Also, relevant to Twilight Despair 5's post below, Lilith was actively breaking seals in season 4. It wouldn't help to leave footprints all over the place. The fact she actually managed to outplay the powerful, if unsuspecting, angel footsoldiers probably means her lack of omens benefited her to great effect.

But I still think it's meta-related. Writers' strike in season 3 and everything.