Might be a mobile app / EU-based account only thing, but I've seen it numerous times and I'm almost certain I've seen it on the web version of Gmail too.
There's a pretty long waiting period before it does this. I'm not sure what the time required is, but I think it's at least 3 months. And it only does this if you don't interact with the newsletter at all.
Just speculation, but it's possible if you also use a non-web/non-gmail-app client it might suppress these notifications.