The main reason they are removing it is because no ads run on groups and they need us to be on the main feed.
“I really want to be able to just have this app to keep up with friends and not have to actually go on Facebook. But the app is currently pretty terrible and it drives me crazy,” one reviewer wrote. via Why Facebook had to kill its Groups app
I would agreed this is the sole reason why I’m still on Facebook. It’s for the groups. I do not have Facebook main app but I have groups app. It’s helps me connect with like-minded individual.
And I would also echo that the main reason that Facebook is killing the groups app is because people are using it and staying away from the main feed which are flooded with ads (very important) and also unnecessary “status” update.
By removing groups app, it helps to reduce additional resources to maintain the app and also “force” people in using the main app.