> What can browser developers even do about this, block all requests by default (therefore making it a feature almost no one uses)? Chrome doesn't even have a setting to block all requests.

Missing the point. This is actually a useful feature, and is part of the big service workers push. The fact that some sites are using it poorly (to say the least), is on the sites themselves. As it has already been pointed out, you _can_ disable them on a per-site basis, and at least on Safari, the same site won't ask again if you said no once (Preferences > Websites > Notifications).