Comment by nelgaard

It it not just because of underlying OSM data.

Navigation apps such as OrganicMaps and OsmAnd filter OSM data, and package it in way that takes up less space. I.e., it will omit individual trees, manholes, etc. It also omits tags from OSM objects that it does keep.

This is all to to make it possible to fit enough maps on a phone and also there have code that can use that data (for searching and displaying)

Take for example Motorhome stopovers (I have edited at lot of those). OsmAnd has name, opening, hours, power_supply, fees, dump_stations, toilets, showers, phone numbers, website, and a few more tags. But not water_point (although it has drinking_water which is not used much for stopovers).

OrganicMap has much fewer tags for motorhome stopovers.