People with small capacity phones (a lot of people) won't install your app, and may actually uninstall it if it's too big. That may not be priority #1, but it certainly deserves some consideration.
However, the cellular size limit is now 250 MB IIRC, so Facebook seems to stay just under that.
These older phones are way more common outside of the US and even just outside of the SFBA where not everyone buys a new $1000+ phone every 2 years.