Have you compared Google's and OSM's maps of those locations side by side? I wager OSM has much more detail. This is the case even for public parks located in the middle of major American west coast cities (where I would expect Google to have good coverage, if they had it anywhere.)

Consider for instance this city park in Seattle:

https://www.google.com/maps/@47.6397466,-122.2948284,18.95z

https://www.openstreetmap.org/#map=19/47.63987/-122.29488&la...

Google has gotten better in recent years, it now has a few of the walking trails, but compared to OSM it's still absolutely pitiful. Even in high profile locations like Yellowstone National Park, Google Maps is pitiful compared to OSM:

https://www.google.com/maps/@44.3925569,-110.5541906,18z

https://www.openstreetmap.org/#map=18/44.39273/-110.55472&la...