But it has nothing to do with to be forbidden to talk to a celeb in a "diva" sense, it's more about security and organization, and F1 has most of the strictest organizations, at least to the ones I attended a couple of times. The grid is the busiest area, racers, reporter people, hostesses and mechanics are moving up and down and even behind the grid, it's just frantic. Now add to that a celeb and to be interviewed, to be allowed on the grid for a certain amount of time and other team garage for publicity etc (say MF in front of the RedBull car, all organized in a very short time) and then moving the celeb to another place to watch the race etc. Basically the staff approaches a celeb, one moment of distraction and before you know it you can get knocked down by a car or get your sandal tangled into a wire (the latter happened to me at the Monaco Grand Prix in 2011) and it all goes down and they all get the blame and here comes the lawsuit etc. Crazy perhaps bt it's all about security.
The staff can happily talk to them at an after party or else but when the race car is on, there is no chance or then very small chance.