You act as if veteran suicide is something that only started in the last few years when, in reality, it's been an issue since the dawn of war itself--merely exacerbated by the fact that our current military operations see these veterans forced to take human lives for no discernible purpose.
In World Wars I and II, our soldiers were fighting to keep the enemy from expanding to engulf all of Europe (and the Pacific). Naturally, it doesn't take a lot of stretching to want to fight to stop such a threat, and it's a good thing plenty of people did just that, too.
In Vietnam, the 2nd most questionable war we've been in, the goal was (supposedly) to stop the spread of (so-called) Communism. Even if the story was a farce, it was a cause soldiers were willing to kill and die for. At least, some of them--this is when suicide became especially prominent due not only to gruesome new tactics, but also the draft. Not fun times.
In Desert Storm, we were fighting to stop a ruthless dictator from expanding his power and genociding the crap out of his people (See: World War II), and like with the two World Wars, it's a cause that's easy to get behind. Don't want that guy to get too much power, or life's gonna suck pretty much everywhere.
The current wars in Afghanistan and Iraq were initiated to put a stop to specific people, yet the war machine is acting as if we're fighting a traditional battle, gunning people down en masse--this is where the veteran suicides started getting REALLY out of hand. Now that the two major villains of these wars, Saddam Hussein and Osama bin Laden, are gone, we should have packed our bags and gone home, but the action has been protracted to ridiculous lengths for no good reason whatsoever. Meaning, our soldiers are currently killing and dying for an already-achieved goal, and everything since that point means nothing. I know I'd be feeling sick and disillusioned if I were forced to fight for my life every day for the glory and sake of nothing.
Point is, too many politicians (a lot of them on the Republican side, no less) are pushing to keep these pointless military movements going indefinitely with no clear goal in sight, while amassing as much money to inflate the military budget even further ($800,000,000,000 a year right now), and all the while, the soldiers forced to trudge along to their oblivious whims suffer for it.