Casey Reas and Chandler McWilliams asked visual designers why they write their own software and how it affects their process:
The answers reflect the individuality of the designers and their process, but some ideas are persistent. The most consistent answer is that custom software is written because it gives more control. This control is often expressed as individual freedom. Another thread is writing custom software to create a precise realization for a precise idea. To put it another way, writing custom code is one way to move away from generic solutions; new tools can create new opportunities.
Most of the interviewees are media artists, but there are a couple of names you'll recognize. My favorite, Amanda Cox, uses a Mad Libs metaphor:
Mad Libs is a game where key words in a short story have been replaced with blanks. Players fill in the blanks with designated parts of speech (“noun”, “adverb”) or types of words (“body part”, “type of liquid”), without seeing the rest of the story. Occasionally, hilarity ensues, but no one really believes that this is an effective method for generating great literature.
I'm looking at you, non-programming statistician.
Update: The article isn't there anymore, so you can read the cached page for now.