I had assumed it was something like “we could cache this locally on the device, but then our telemetry would potentially be delayed, where if we always fetch live from the network then we get to see what they wanted immediately which is better for facebook for (insert reasons)”. The network fetch would be much more expensive in terms of battery life.
Full disclosure: I have had to implement telemetry collection and have faced this kind of trade-off against power budget, but not for social media/personal/phone apps.
