The issue we observed was that people were feeling compelled to visit every like notification or dismiss them to clear them out, and that was not a feeling or behavior we want to encourage.
Once we made this change that problem disappeared and there were no other issues we observed.
It is more difficult to explain, but we haven’t felt the need to do so for except here among the most inquisitive of users.
For those that really want to see all their unread likes easily, the option remains available to do so by going to the likes tab in the notifications menu.