In other studio environments, there can be an uneasiness attending development, a kind of mix-and-match approach that benefits no one. A writer is hired to work on a script, a director is chosen to helm the film, and everyone tries to invest him- or herself in this awkward situation. Executives loom over the whole process and never forget to remind the filmmakers, "If you can't make it work, we have three or four other writers or directors we can call in."
Knowing that movies are never finished, just released, fear is a real motivating factor in doing good work. It's not the typical industry fear of losing one's position, but rather the worry of not living up to one's potential and doing one's utmost best.
During development, it's also important to keep certain trusted people away from the story, so they can review it objectively at some point later in the process. This "brain trust" can see the story with fresh eyes and offer their honest perspective to spark further refinement. There is no back-stabbing, no political wrangling or jockeying. No one is worried about losing their job or spoiling their relationships. It's liberating and refreshing to get constructive feedback in such a mutually supportive environment. Everyone's focus is on helping to make the best movie possible.