I use this regularly when I go on long walks out of the city (including the couple of times I've done stretches of the Camino de Santiago). The offline map support and being able to load and display GPX tracks are really helpful there. Not only because you can sometimes find yourself with spotty reception in remote areas, but also because if you are out all day and your phone battery is not the best, you can just stick on airplane mode which massively saves on battery.

CoMaps also makes it quite easy to edit information about businesses etc, so if you spot something that isn't right you can correct it right there.

Also, for long walks/hikes, OSM is excellent. Most people tend think think of OSM as "Google Maps but worse" but IMO it is clearly superior for this use case (at least, for reasonably popular routes). It will display a lot of paths that Google Maps won't and also has far more granular detail, so you can use it to find nearby water fountains, picnic benches, even bins and so on.