I would assume it also has to do with your assignment and how much/if any combat you’ve experienced and injuries you sustained.
My Dad was drafted into Vietnam - infantry - and was wounded. He was only there ~ 6 months, and tried to go to university on the GI Bill, but for awhile couldn’t stand being in that type of environment immediately after returning home. PTSD/survivor’s guilt, etc, were too much.
Later on in life his injuries prevented him from being able to work. This, combined with rising medical debt, left us in a bad spot.
What you’re exposed to when you serve and when you served also come into play - PTSD is taken more seriously now, as are the effects of things like Agent Orange. I’m not sure if the VA is better or worse from, say, 20 years ago, but that could also be a factor.
Not sure if this helps to answer your question, but that’s my personal anecdote.