Have you tried to visit Facebook from a mobile browser? It works much better, although they don't like to provide native notifications (so you must use the native app, although you don't need it as you have access to exactly the same content).
Mobile web-app doesn't keep any background service running so much less battery draining.
The same applies to Twitter, Youtube or Google+. But their native apps are not as bad as Facebook one.
Future will not be native but web. I didn't like the idea, but today I am a big deffendant of it.
I don't use FB on my phone, however everyone I know who does; uses the Messenger app. The future maybe web, but now is app.
Cg
Oh! I forgot about that. Native Facebook app forces you to download another app, the Messenger to chat. That means having lots more redundant code on their devices.
Facebook has not disabled the access to chats from their mobile site, yet. So: you have both content by the same prices and still are able to save disk space.
I get more that 1 gigabyte after uninstalling both of them.
I didn't say that it's any good; simply that it exists and lots of people use it, that's the point.
Cg