Most scripts that are commissioned or purchased aren't actually made into movies, so that's not as much of a prodigal act as it might seem. The script is probably the least expensive part of the movie, I'm sure I've heard that virtually every screenwriter has made their living more off of selling scripts that don't get made rather than the handful that actually do. Any time you've heard of a movie that didn't actually get made being in development, somebody got paid to write a script for it.
Just thinking about this reminded me that Steve Carell was set to star in an adaptation of my 9th grade English teacher's memoir, a project that, nine years later, has never been heard from again after his involvement was announced. I'm not really sure if Carell could pull off "brutally witty yet kindhearted beatnik," but I had been interested in the prospect of seeing a movie that potentially, would include several characters based on people I knew, and definitely would have at least one.