This isn’t the regular Notifications API, this is more like phone notifications, where you don’t even have to (have the app open || be on the website) for it to work. Uses the fancy new Service Workers.
It requires and opt-in, so it’s only as spammy as you let it be. I can imagine some pretty useful stuff: “Your bus is behind schedule”, “You’ve got a new match”, “Your website isn’t responding”… things you want to know faster than email.