Almost all pages, either by default interface or intention list child pages. These are used to automatically generate contents lists.
When such a Contents page is watched, and children are added, the apparent 'contents' of the page is updated, but the users are not notified. this is NON-INTUITIVE to most casual users. This is a problem with other forms of content, such as includes, but for children, there should be no use case where a direct child is added in that a user watching a specific page would not want to be notified.
So until a grander (and more difficult) CONTENT NOTIFICATION rather than EDIT NOTIFICATION improvment is made, please implement:
"Adding a child page triggers a notification event for it's direct parent".
(this can be a site or space configuration item if you like)