But it is now available with Google Maps! View some location in Satellite mode, and then click the "3d" button on lower right. And then you can view any place from various angles
Looking at 3d google maps a bit more closely, it does seem they are capturing the sides of buildings that are not visible on the top down image. Still nowhere near the quality of Birds Eye, but I'd be interested in what other image sources they are using besides top down, and how they are captured.
For example, take an airplane and mount two cameras on it, one on each side, angled down at perhaps 45 degrees to capture ground imagery in each direction.
Add a LIDAR device next to each camera to capture a "point cloud" of the same area the camera is imaging.
Now you have photographic images with distance data for each pixel. You can use that to construct a 3D image that can be viewed from various angles.
(Disclosure: I work at an unrelated Alphabet company but have no personal knowledge of any of this, it's just my semi-educated guess.)
However your comment made me think of this awesome article about Google maps and 3d buildings https://www.justinobeirne.com/google-maps-moat