It looks like Clear Channel/iHeartMedia did own the station the entire time, though past entries on Wikipedia for WWKZ state that URBan was the owner of the station [roughly] from 2007 to 2015; I guess owner and operator weren't distinguished here, despite it being the case in Wikipedia pages of some other radio stations.I don't remember when it happened, but you're right that it happened without making any headlines. From what I remember, the deal to URBan never ended up closing, and URBan operated Tupelo and Meridian under an LMA. That might've been why the deal falling apart didn't make fanfare. iHeart found a new buyer for Meridian but not Tupelo.
QMFM in Vancouver and Bob FM in Winnipeg were strong brands in their respective markets, with the former having a lot of heritage. Yet they changed branding whilst they were on top.For some, like pointed out before, heritage rules. No need to change KDWB or Z100 to match a national brand.
For others, it's because there might already be a station of the name they want to use in a market. KISS-FM is a rock station in San Antonio. There are Country stations that are "Kissin' Country" that would probably put up a fight for the name in other markets.
So unless the company wants to come up with a totally new brand and force it across all of their stations in all of the markets, it's tough to do currently as it is.
iHeart gets around that though by basically never having the tracked jock ID the station. Any station ID is done via imaging etc. Kind of like how Bru or Julia on Audacy's CHR's across the country handle things.
If iHeart were to do mandatory national branding, I can imagine them giving names like iHeartCountry. They may need to use brands other than Mix, River, and the like.
Oh, and many tracked radio personalities do say the station name, though in a scripted manner (e.g. "Listen to [radio station] on iHeartRadio. Download the app or go to [website].")