Release and design teams also don't want redundant apps in core, and
there is interest in somewhat reducing the number of apps in core. We
had been planning for several years to remove eog (obsoleted by
gnome-photos and to remove evince with gnome-documents. Now it looks
like gnome-photos and evince will be the winners instead. (eog is a
very nice app, but once gnome-photos gains the ability to handle
images, it becomes kinda redundant, right? I only hesitate due to
nomenclature: not all images are photos. Maybe gnome-photos needs a
rename.)
Removing Evince would have been slightly complicated even if Documents were developed more heavily than it is because Evince is used for the print preview in every GTK application, and nobody ever considered writing the equivalent functionality for Documents in the first place.
Ciao,
Emmanuele.