Because some writers are cowardly assholes.
"Teju Cole, Peter Carey, Michael Ondaatje, Taiye Selasi and other writers have decided to withdraw from PEN American Center gala honouring staff of Charlie Hebdo. In an email interview with the New York Times, Carey questioned whether the Charlie Hebdo case was something PEN, established in the 1920s to encourage free expression and solidarity among writers, should even be involved in."
So fuck you.
I would from this day on, not read anything from these assholes again.
Pen got it right. Freedom of speech mean all writers have the rights to create what they like, without censorship, and without the threat of being murdered.