It could be Fox hates to interrupt their programming, but I think it is because they hate to get it wrong, as initial reports usually are. Every time Fox has something wrong they get hammered, so, they verify before going with initial reports.
Just my thought, as the MSM and their hounds attack at the slightest Fox error, whereas all the other networks and CNN are given a pass.
Maybe thats all true, but FNC does a piss-poor job on breaking news more often than not.