There are so many companies these days doing recording for self driving cars and/or street view like applications. Also sites like Flickr collect huge sets of geo tagged photos, as do companies like Meta where tons of geo tagged images are shared each day via their different outlets.
Niantic has the benefit that they can steer "volunteers" to specific points, though.
Maybe Niantic intentionally steered players towards remote locations only reachable on foot, understanding that this data is more scarce and therefore more valuable?