Leaving aside for a moment who is and is not civilized, there's at least one point where a person's self interest and their government's interest in secrecy might align in suicide: when the agent is faced with torture. The agent would want to avoid serious pain that might end in their being killed anyway, and the government would like to keep what secrets they might reveal. Without fanaticism, there is pain I would die to avoid.
As far as the West being an enlightened civilization, Alberto Gonzalez' defense of U.S. torture relevantly suggests to me that civilization only goes so far.
So unless you want operatives that are unstable and not too smart, suicide pills will never be used.