This was an example of where web developers really should've known better in advance. They literally coded an intentional new way for people to make popup ads, and it's the primary use of the web notifications API.

I regularly hear of complaints about spammy popups on people's computers, even when they don't "have the web browser open". And it turns out it's just stock Google Chrome, doing exactly what Google Chrome was designed to do: Pop up ads, that everyone has since started shipping ads through.