If the premise is correct, then what's the answer?:
Cowards, every single one of us?, by Chris Blattman: Early in the 20th century, the West’s intellectual elites rushed to fight the Spanish civil war. The same could be said of World War II. It’s hard to imagine the same today. What happened...: why doesn’t this generation’s intellectuals fight this generation’s wars?
Cowards, every single one of us? Possibly, but I see a few other explanations.
The economist in me says it could be comparative advantage at work. Technology has played an increasingly important role in war. A sensible government would direct its best educated patriots to engineering and intelligence.
The armed forces also face more competition for idealistic talent. We’ve seen 10,000% growth in the number of international NGOs in the last 60 years. Those who want to fight injustice have many more options.
There is also the perception, probably real, that the army is no longer a friendly place for intellectuals. A consequence of competition and comparative advantage?
Three generations have also witnessed the examples of Gandhi and Dr. King, and the gospel of non-violent action. ...
But the answer that appeals most to me: today’s battles are not drawn along intellectual lines, but religious ones. The Spanish Civil War was the left’s stand against fascism and the subjugation of the European working class, and the way the West would be run. There is a battle for hearts and minds, but not within our own society.
The Vietnam war was not a religious battle, it was portrayed as an ideological battle against communism, yet the intellectual elites did not rush to join the battle, so I'm not sure the last answer explains the change. But I don't have anything better to offer, so I'll leave it to all of you to resolve whether the premise is correct and, if so, why this change has occurred.