If not then that is the use-case for SQLite.
It could still collect data to the server on a delayed basis for the benefit of the app-owners and for back-ups but that is not time-critical.
Lots of things predictably don't. It seems like bad engineering to operate as though everything will. Especially in appliances/"IoT" and other embedded use cases, that line of thinking can drive production costs up a lot.
In the context of embedded things of course you should use something like SQLite as opposed to postgres, because there aren't going to suddenly be millions of people using your CO2 monitor (for example). But for web stuff you can plausibly have user counts that span 6 or 7 orders of magnitude, so you want to be prepared for that.