It's deliberate - Gaddis did not like publicity and did not want to be a celebrity. Here is part of his reponse to winning the National Book Award for JR in 1975 [1]:
"... I feel like part of the vanishing breed that thinks a writer should be read and not heard, let alone seen. I think that this is because there seems so often today to be a tendency to put the person in the place of his or her work, to turn the creative artist into a performing one, to find what a writer says about writing somehow more valid, or more real, than the writing itself.
... it seems to me the only way to keep writers writing well, or trying to write well, is to read what we write."
1. in The Rush for Second Place: Essays and Occasional Writings (2002)
