Why the fuck does a newspaper need a ‘notifications’ icon in the top right hand corner?
Because it has an updating-feed-like structure, in which new items can appear.
Knowing that there are (N) new items is so useful (to some people), that as far back as the 1990s, we developed technology called "RSS" to give you this superpower over a website that doesn't provide anything of the sort. One that simply updates with new stuff when you hit refresh, with no UI to indicate what is new/changed.
How else can they report on BREAKING NEWS if it doesn't at least break your concentration?