While it is always possible that they just massively suck at infrastructure, I suspect that cheating is the issue preventing more caching.
By keeping everything on their servers, the types of cheating you have to police are massively reduced.
And people who play Pokemon will do ANYTHING to catch 'em all.
Another user has already mentioned they don't attempt to cache image or textual information about Pokestops. Pokestops for most people are pretty recurring. This probably consume less information than the models but is also likely to be pretty static information.
Could you provide a source for this? I did some Googling but could not find any information supporting this.
I definitely agree on the Pokestop data, but I find it hard to believe that models and animations are not assets included in the app file.
If you were Niantic, and expecting Pokemon Go to be roughly as popular as Ingress, would you bother going to the effort of adding a caching layer when you could not, and expend your efforts on the front end and content, and get the release out sooner?
Because Ingress wasn't reliable either, and this way Pokémon Go has an opinion of being playable mostly when everyone else is asleep. It's only this week that I can actually run it somewhat reliably after work...
Speaking of Ingress portals - there were not much more dynamic than Pokéstops are (given that you can drop "Pokéstop modules" on them, which affect all players). This was my complaint against Ingress too - while portal state should be redownloaded continuously, the visual/information data changes infrequently to never. The name, the photo. The stuff you actually need to have to display portal details. Similarly Pokéstops. That kind of data should absolutely be cached. It cannot be used for cheating, and caching it is like elementary engineering.
There's a good chance players will click on the same pokestops again and again, so caching even just the last 50 one would be helpful.