I feel like one word is a rudely short answer but that's it. Offline maps, open data, open source application... that's my thing.
Also, from https://support.google.com/maps/answer/6291838?co=GENIE.Plat....
> Note: Downloading offline areas isn't available in some regions because of contractual limitations, language support, address formats, or other reasons.
Yes, Google can't provide offline maps in some countries. This is true of all mapping applications, though some have better offline coverage than others, nobody has everywhere. For example HERE does not offer offline maps in Japan or South Korea.
Compare that to the 179mb/113mb that I need with OSMAnd/Maps.me for the whole country without fiddling. Add to that the fact that OSM's data is significantly better than Google Map's for my country (YMMV) and that there's no such thing as "offline mode not available in some regions" with OSM.