"No one else has anywhere near the richness of data (and metadata) that Google Maps has"
That will be because they are charging people to put listing there, and scrapping sites like yelp, tripadvisor, and other such databases. Once you get an effective monopoly you can start charging.
In the early days of GM they scrapped images with geodata from flickr to tart up their map pages. Their streetview pages contain still images, the photographer won't have licensed their images for that. I know because I've found a number of my photos on streetview and there is no way to get Google to remove them. Except by kill the flickr URL and removing metadata. This is one of the reasons why you won't see any of my photographs of Google Images they are robot meta banned from indexing my site.
Put site:professor-moriarty.com into a GIS and see the difference in a bing images search. Its not perfect theycan still show up if they are linked to from elsewhere on the web.