Well, I think it would be kind of hard to get people to give up their lives at such a young age for something so mundane as making rich men richer, so of course the young soldiers believe they are dieing for a noble cause.
That mistaken belief doesn't make it a noble cause.
The U.S. has been involved in perhaps 100 wars since it was founded; you could count on one hand those wars that could be said to be for a noble cause, and you'd still have some fingers left over.
The 7th Cavalry under Custer's command was wiped out to within a man on June 25, 1876; the "noble cause" these soldiers died for-- the "freedoms" we take for granted-- was to steal the Black Hills from the Lakota after we had signed a treaty that guaranteed the Black Hills as part of their Great Sioux Reservation. That, and George Armstrong Custer wanted to use the campaign as a springboard into the White House.
The Mexican-American War? The "noble cause"-- the freedoms" we take for granted-- was the theft of half of Mexico.
The Spanish-American War? The "noble cause"-- the "freedoms" we take for granted-- was the theft of the remaining Spanish Empire for ourselves.
And so on. Young soldiers died needlessly, and the justification for those deaths isn't base greed, it's a "noble cause." One can regret the needless loss of life at Gallipoli, in Vietnam, and the Little Big Horn without buying into the propaganda that says they died to give us freedom.