I haven't paid close attention recently, but my understanding is that government datasets do get imported to OSM—but they're not perfect and still require some

I haven't paid close attention recently, but my understanding is that government datasets do get imported to OSM—but they're not perfect and still require some amount of clean-up. So it's never as simple as downloading a file from the local government and uploading it to OSM. Drawing house by house may not be the most efficient way to improve OSM in the long term, but it has lower skill requirements than sanitizing and validating a third-party dataset.