No. The simple fact is that it is NOT true.
Even when upper-class youths did go to the front (enforced more by social mores than government force -- as you correctly point out, the people in power will never really be effectively subjected to the latter), nations willingly marched into the meat grinder (World War One is a textbook example: a "war of choice" that could have easily been avoided if multi-digit IQs and multi-second attention spans had been in charge. It butchered an entire generation across all economic and social lines.)
Why not, exactly? I'm not sure what your point about WWI was, other than to point out that once upon a time, upper class types volunteered be officers, in order to send poor grunts charging at entrenched machine guns.
Regardless, America, 2006 is a long, long way from America, 1917. Back then, everyone knew someone affected by the war. Nowadays, outside of more conservative circles, it's pretty rare. For most of my civilian friends, I'm the only one they know that's been to Iraq, and they consider that quite a novelty. Knowing a WWI vet in 1921 wasn't considered novel in any way.
It takes a lot of faith in what you are doing to risk your life. It takes a lot more to risk your kids.
Chairman Mao had a son, Mao Anying. After the onset of the Korea War, Mao's son went to the frontlines with the People's Volunteer Army, where he was killed by a U.S. airstrike. Mao may have been a cynical old bastard, but the loss of your eldest son hurts a proud Chinese leader on many levels.
I somehow don't see President Bush being so ready to "stay the course" or "leave that to the commanders on the ground" if Jenna or Barbra were, say, captains in an MP company. I don't say that to imply President Bush is a bad guy. I met him, briefly, while I was in the Army. He thanked me for my service, and I believe he was 100% genuine about it. It's just not the same. No one in his inner circle, except Ashcroft, I believe, had any direct blood in the fight. You can feel bad about the fears or loss of others, but it'll never really ring home until you risk or lose your own blood.