"Those suggestions shaped the law, passed in 1997 after the sad experience of Gulf War veterans. Tens of thousands of them waited years before getting the government-provided health care they earned as soldiers. Why? A lack of basic health data delayed a Pentagon decision that their maladies -- now known collectively as "Gulf War Syndrome" -- were related to their service"

Most likely the same reason why they're doing it again.

The humiliations the troops with Gulf war syndrome had to go through on both sides of the Atlantic for recognition for their illness was disgraceful. They were treated like money grabbing liars. (Though, if I remember correctly the Americans recognized the disease before the British did, the British government treated the sufferers like scum.)

Once they can no longer use you are only a drain on their resources. The less court cases and compensation the Government has to deal with, the better.
With this example any troops with a complaint will have a much weaker case as they do not have a comprehensive medical check to correlate their case against. The Government's learned its lesson from the last time. Only, as always, it’s the wrong lesson.
That's what it looks like to me.