True story:
When KTAR in Phoenix moved from 620 AM to 92.3 FM in 2006, they spent huge amounts of time and money promoting the move, during a two-and-one-half-month long simulcast.
On January 1, 2007, KTAR-AM went all-sports.
The AM ratings stayed high. The FM had trouble gaining traction. It went on for a year. Finally, Bonneville did some research---and found that a significant number of the KTAR audience never switched to the FM.
Because KTAR-AM had always had a significant sports presence (Diamondbacks, Cardinals, Suns, ASU), people interviewed said they tuned into the AM, thought they must have tuned in during a game, a pre-game or post-game show, stuck around to hear the talk show they expected---and when it took too long, turned it off.
Bonneville spent another boatload of money and finally got the full talk audience over to the FM.