I think its because of a lack of purpose, of a cause. The military, you always have a mission, something to DO. Civilian life requires that you provide YOURSELF with the mission, purpose, something to do. Without purpose, why be alive?
I think what you hit on is important to consider in many ways. Remember, our military are overseas in combat areas like Syria, Afghanistan and Iraq and losing their lives there. How many of those men and women have questioned what their real purpose is being there?
We haven't fought a real war for our 'freedom' in more than 70 years. How can men and women be considered heroes when they're ordered to drop bombs from helicopters onto trucks loaded with civilians as happened during the Iraq 'war'. We can't just put a man or woman in uniform and expect them to have a committed patriotic ideology. When we attacked Iraq to get to Saddam Hussein, he was defeated in a relatively short amount of time. But then the US brought more and more soldiers to Iraq to protect the oil fields. The U.S. got criticism from all over the world and never received long-term NATO support for this action. The invasion of Iraq was a shame for NATO as an organization because the USA said, Hussein had 'weapons of mass destruction' and had to take action. The U.S. tried to drag NATO onto an extended occupation and some NATO members that had committed to the initial invasion quickly realized the USA had fooled them. All the U.S. wanted was the oil and they secured it quickly. While NATO forces quickly departed after Saddam Hussein was captured, the U.S. remained a presence.
The USA hired a lot of mercenaries, retired veterans, that were once in the US Amry but now worked under contract which means, they're soldiers fighting for profit. They earned as much as 450k in 2 to 6 months. These mercenaries are not under the limitation of regular USA Army because they're private so what a soldier cannot do as regular US Army - they can do as a hired army. They literally got into little helicopters and made it rain. They fired hundreds of rounds of ammo over innocent people. These were Iraqi people who had nothing to do with Saddam Hussein. Children, women, men in the suburb areas that weren't even part of a war zone. These hired soldiers killed as many as they wanted. if you might be thinking "oh so that's why so many were pissed off and joined Al Qaeda." Yes, that's exactly why so many people joined Al Qaeda. The similar thing happened in Afghanistan. Al Qaeda was born, just as it was in Iraq. If they pull the same move in Syria, don't be surprised if another 'terrorist group starts in Syria.
Does anyone remember Chelsea Manning? "Formerly Bradley Edward Manning, Chelsea Manning is transgender and was a 'whistle blower' uncovering many incidents involving fellow soldiers while assigned to Iraq during that 'war'. He obtained information through Wikileaks which contained hundreds of thousands of classified documents in what was believed to be the largest unauthorized release of state secrets in U.S. history."
https://www.britannica.com/biography/Chelsea-Manning
[snip] In February 2010 WikiLeaks posted a classified diplomatic cable that had been dispatched by the U.S. embassy in Reykjavík, Iceland. It marked the beginning of a flood of classified documents, including the April 2010 release of a video that showed a U.S. helicopter crew firing on a group of people that included two Reuters employees.[/snip]
Chelsea Manning is transgender and served time in prison as a whistle-blower, uncovered multiple incidents of fellow soldiers laughing as they murdered civilians. Keith Gentry, a former Navy man, wrote that when he and his division were bored they preferred passing the time with the “entertainment” of YouTube videos capturing air raids of Iraq and Afghanistan, often making jokes and mocking the victims of American violence. If the murder of civilians, the rape of “brothers and sisters” on base, and the relegation of death and torture of strangers as fodder for amusement qualifies as hero.
More on Wikileaks, Chelsea Manning, Iraq, Guantanamo, etc.
https://www.britannica.com/topic/WikiLeaks#ref1108470