I'm certain Joss Whedon and J. Strazynski do the same on their shows with their writers and actors.
It's funny that you mention Straczynski, because here is a guy who has killed shows because he wasn't allowed by the powers that be to stay true to his original vision. Crusade and Jeremiah were both killed because of creative differences with the studio. That isn't to say that he didn't allow the actors their say. G'Kar, played by the late Andreas Katsulas, played G'Kar. Initially G'Kar was to pronounce the G as a hard G, so it was supposed to sound like Gukar. The actor introduced the character on film with a soft G sound, so it was more like jekar. When JMS asked Katsulas about it, Katsulas responded that he'd decided he was French. JMS liked it so much that all of the male narns had the je sound at the beginning of their names. That is an example where someone brings something interesting and makes it part of the larger universe, thereby adding some flavor and originality to the setting. Now if Katsulas would have come to the set dressed as a klingon and said that his character will be a klingon, he would have been told off for wasting a day of filming by making his makeup artist dress him up as a character that doesn't exist in that universe.
But where JMS was fine with allowing a certain amount of improvisation with his actors, he doesn't tolerate studio interferance. With Crusade, the studio wanted him to amp up the sex and violence and turn it into some sort of stupid WWF in space. When he couldn't work out the show he wanted, he wrote and filmed a couple bad scripts that he knew would piss off the studio and killed the show. I can't say I blame him, frankly. In season 2 of Babylon 5, the studio wanted him to create a hotshot pilot character because they thought it would appeal to a certain demographic. He did so, but then he killed the character at the end of the season. After B5 was over, he killed Jeremiah after two seasons because he couldn't deal with the studio's demands. On the other hand, he hasn't had the same problem with Spiderman and the other comics he's been writing because they aren't his characters, and his stories are still secondary to the universe that he's been hired to write in.
How this relates to a DM is that if a DM has created a unique world and he already has a massive campaign that he created and is going to run, then he has the right to tell the players what does and does not exist in that world. It's his world, it's his story. Telling me, the DM, that I have to allow a tiefling character even though the world I created doesn't even have demons would be like Katsulas in the above example coming to the B5 set in a klingon outfit. It doesn't work and I don't have to allow it. On the other hand, if I'm running a Forgotten Realms game, where everything is intentionally present by the setting's designers, then the only reason I would veto a character race or class was if that race or class is overpowered and broken. In such a case, I would likely offer to redesign it for the player so that it wasn't broken. This would then bring into question whether the player wanted this character because playing that race is a cool roleplaying concept or if they were just being a power gaming munchkin.
Finally, knowing that there is a great deal of power creep in the splat books, I was always very reluctant to allow material from them into the game. I would always look at it first before approving it, and I would always retain the right to reject anything that I thought was too good. In fact I warn players from the beginning not to invest money into splat books if their expectation is that I will allow it into the game. I'm more of a stick to core, with certain exceptions, type of DM. If the players know that up front, before they even show up for the game, there isn't a problem.