I'm not sure about domestic policy, but being military is definitely a boon for people studying security studies, as they can call bullshit on unfeasible, impractical, or implausible ideas that sound good on paper. It's part of the reason I switched over from my political science PhD to a public policy oriented school. So many stupid ideas fly-by but because professors have credentials you don't and other students reflect those same biases, you can't call them out, despite you having personal experience in a particular subject.