The license for F1 is complex. They can put the Ferrari F1 cars* in this game but cannot take part in events as this would constitute GT having F1 races which isn't allowed as codemasters have the rights to an F1 racing game.
The F1 cars are there for 'show'. After what PD have done with the NASCAR, JGTC and WRC licenses, (Clue = Not very much) it's probably best they let someone else have the F1 racing license...
*(Ferrari get special permission to license their cars as they please, unlike the other teams who are tied together 'as one' to the F1 license which codemasters currently have)