Not only that but lwn is one of the main sites that gets submitted to HN all year round (not daily, but maybe nearish to daily). So the audience here on HN has been exposed to it over the years. I'm not sure what more they could do to get new subscribers, I certainly hope they figure that out or how to get new ways to earn revenue without having to go the ad route.
That's the thing though. You can get all the value from LWN through here. Even if it wasn't for them tolerating subscriber links being posted on HN, the week-long delay isn't nearly enough an incentive to actually subscribe, rationally speaking.
I’m occasional lwn reader and I had no idea there are subscriptions there!