It's interesting that the sites that you'd expect to use notifications tend to not be the ones actually offering them. Webmail? Reddit? HN? Obvious notification cases. Legitimate ecommerce? I could see prompting for "let us send order update notifications after purchase." Don't see it there though.

Instead, I see a lot of "enable notifications to prove you're not a robot" scam fake-CAPTCHAs and a lot of newspaper/TV/media sites asking for it. Just because I want to read one article doesn't mean I'm naturally after an update every time you post anything else.