Maybe I’m being too charitable, but I suspect it’s down to a few requirements: instantly/universally recognizable to drivers, easily visible from the street, located on corners, and always pronounced correctly by the maps voice.

Fast food restaurants and other major chains fit that bill reliably enough that you could automate adding them to directions. Telling drivers to take a right at, say, a local restaurant that may not have an obvious sign could easily be worse than relying on street signs.