I guess I'm saying that the celebrity nature of actors is a confounding factor. It's not that these actors are merely celebrities among the film industry, but your mom and dad and friends actually have heard of them and their presence in a film is going to influence whether or not people turn out to see the film. You can get the most famous programmers together to build a product, and no one is going to buy that product on the basis of those programmers' celebrity unless some segment of the software industry is the target audience for that product.

To be quite clear (and likely this was your point, in which case I agree), if the film/tv unions excluded actors, the effect would be pretty comparable. My friends and family aren't going to see a film because Joe The Sound Guy worked on it just like they aren't going to buy an app just because Collin The SRE worked on it (no matter how famous Joe and Collin are in their respective industries).