It probably doesn’t hurt to mention them here, but you probably also shouldn’t go hunting for them.
There are a number of cities that have zero streets because their OSM record was deleted. Some of these may have had streets at one point, which results in there being people listed as progressing it. Others may have never had streets, so there’s nobody present in that list.
There is another set of cities that have zero streets because a recent update cleared them for some reason that I have yet to figure out.
Day over day, I’ve been pushing zero-street cities to the front of the queue. It’s down to around 150 that may or may not have a corresponding OSM record. I’m slowly going through those to see what I can fix up.
I have been removing cities that no longer exist in OSM, but I’ve recently second guessed that … Perhaps if the dead link still exists, someone may be able to re-add them if they were accidentally removed.