They don't want their top brands associated with the NFL. They still have the time but will do other things with it.
The Anheuser-Busch move follows a similar announcement from PepsiCo., which won't be advertising its biggest brand, Pepsi, in order to focus on its sponsorship of the the halftime show. (It will be advertising Mountain Dew and Frito-Lay products). Other veteran Super Bowl advertisers like Coke, Audi and Avocados from Mexico are sitting out the game altogether.
They don't want their top brands associated with the NFL. They still have the time but will do other things with it.