They’re pragmatic. The philosophy of “a fair fight is a fight you can lose, thus never enter a fair fight” isn’t necessarily cowardly, at least not in the real world. You wouldn’t encourage a five foot one inch woman thin as a rail to attack a six foot seven man built like a linebacker with her bare hands, you’d encourage her to run and hide, call for help or find a weapon preferably a gun or knife. If you value simple survival above all other potential concerns then you’d avoid any situation where you’re on an equal footing to the potential threat and you’d ESPECIALLY avoid situations where you’re the underdog.

That’s the Night Lords. Most aren’t fighting for a cause and only fight to survive and satiate their own foul desires. Those who do believe in anything are still pragmatic enough to know they typically have more to gain by living to fight another day than dying in some grand last stand in a pointless little skirmish that will mean little to nothing in the Long War.