Quite simply they fought because they were young men - but mostly they fought because they were drafted. By 1864 the desertion rate in the Confederacy was devastating.
I can certainly agree with this, although I'm not sure it adequately explains the initial surge of volunteering. Interactions of southern honor, evangelicalism, etc. as explored by Bertram Wyatt-Brown seems to help, in addition to the factors you listed above, though.
Another poster commenting on what I guess we can now call the Civil War in historical memory seemed to suggest that there is an ever-present need to rationalize our ancestors' participation in the Civil War. As if slave-ownership were a necessary pre-condition for enlistment, and fighting in the Civil War rendered one a de-facto reprobate. My point was simply to illuminate how ridiculous a statement that was, and again, how much more complex soldiers' motivations were.
If anyone is interested in the subject James McPherson has an interesting book, "For Cause and Comrades," that goes into all this stuff. He posits a tri-partite division of motivation: "initial," "sustaining," and "combat." Good stuff.
This post was edited on 11/22 at 11:39 am