Yes, the reason is...it is easy.
Yeah, it's called money. The NFL starts their Sunday games at 1:00 because of church. More eyeballs on tv sets after church than during church. That means more money.
I wouldn't want to have a lot of them, but one of the things 9:00am games could help with is exposure for the conference. The conference has complained for years about a lack of exposure because back East, everyone is going to bed when the PAC games are starting.
So when teams are playing 9:00am games here, they will be noon games back East.