[interestednovice]

I imagine for the sake of the NC.

They would have to take extended trailers, an extra weather forecast or a final (borderline irrelevant) BBC London bulletin (because that’s the feed the NC takes during Breakfast) if the regional news was just before 9. By having it just after 9, the NC has conveniently “already left” the broadcast, and it also allows those getting up late to see a proper summary of the news - this way, if you switch on at 9, you get TOTH headlines, some coverage of the top story of the morning, plus a regional headlines summary within a few minutes. You lose that “overview” if you have the regional news before 9 - and, although this might not be something featuring in the minds of many regular Breakfast viewers, a lot of people do get up late!