"It's always money."
James Joyce, "The Thin Red Line". Altruism is an interesting concept, financial gain is a fact.
I'll look up that book when the stack by my bed gets a bit lower. Another great read on a similar subject is "The March of Folly", by Barbara Tuchman.
She analyzes the similarity of the political reasons for three great follies -
The Reformation, and the way the Popes arrogantly tried to put it down rather than hear the issues,
The American Revolution, and the way the British MPs arrogantly tried to put it down rather than hear the issues, and
The Vietnam War, the way America got trapped and couldn't stay in, and couldn't get out.
She has a fourth, the Trojan Horse, but I didn't see exactly how that fit. She does, I didn't.
Arf.