The assistant is one of the most important institutions in Hollywood. Every executive of any "importance" has an assistant who answers the phones with "BLAH's office" (as in, "Ben Fritz's office," if I was important), handles their schedule, and does all the other boring work, including, if they're a bit of a jerk, sending flowers to relatives on their birthdays.
What does the assistant get out of it, besides the excitement of a being screamed at and sexually harassed? The knowledge they get from watching their boss at work, the contacts they make from listening to his or her phone conversations, and the referral they are supposed to get from their boss one day for the job they really want.
Right now it's a mutually beneficial economic system. But technology could make it obsolete one day. As this video from Beet.tv (via Engadget) demonstrates, Microsoft R&D is hard at work on virtual assistants. There's still tons of work to do, but "Laura" is capable of understanding when people are talking to her, engaging in basic conversation, and making shuttle reservations. In a few decades, it seems entirely realistic that this artificial intelligence will be improved, and then tweaked by some showbiz entrepeneur, to roll calls, schedule lunches, and take its bosses bad moods with a smile. Hell, it could probably even provide better coverage on scripts than a lot of real assistants do these days.
But how do young people get the training and connections to take the "real" jobs one day? Maybe they don't. Maybe the robot assistants become the robot overlords who rule Hollywood.