Like actors, there are going to be players who demand certain roles and expect particular things from your story. They want loot, they want the spotlight, they want to be spooked, they want tear-jerking scenes or battles that put their favorite films to shame. As a DM, you have to keep them satisfied or it's gonna suck because nobody wants to play in a game they don't enjoy. And, yes, there will be a prima donna or jerkass player from time to time, and you need to decide how to deal with them.
Improvisation, as stated earlier, is also key. Some soap operas do multiple shoots of a murder scene to prevent anyone, even the actors, from guessing who dun it until the final reveal comes out. Sometimes when time needs to pass for the plot to develop further, or as a break from high-tension scenes, you have filler. Sometimes you have to ask someone if they’re sure, like calling for the tape to stop and asking them if they really want to put that on film, but ultimately, even though you can tell the players ‘no’, it’s not always reasonable or fun to do so.
Ultimately, the DM does get a particular benefit no producer does- his audience is made up of his actors. Instead of having to answer to a network, he gets to fudge scripts or let the player run with an improvisation while pretending everything is going as planned. He doesn't have to appeal to any other demographic but the one in front of him. He doesn't have to write the scripts ahead of time to show the show has potential and deserves air time. This gives him incredible flexibility limited only by what he and his players are willing and interested in doing.
When you ask people to sit down at your table, you're asking them to sign a contract, and as such, you have to tell them what the conceits of the story and game are so that they buy into it and are willing to act so you can put on the show they star in. You've got to give them a 'job description'.
That's just my fifty or so cents.