Most of us already have.
On those occasions where I have been asked why I haven't gone (as if the gray in my beard isn't proof enough that I'm not any good for kicking in doors these days) I've asked, "Where were you in the late 80's when I was keeping planes in the air to protect your freedom?" I haven't had anybody even answer yet, they usually just walk away.
I did my time, and I'm proud of it. I'd serve again if called. But this nation needs my wife as a nurse more than they need my pudgy butt wearing a uniform. It's time for the next generation, and they're doing a fantastic job.