I would guess that at least some of this is politically motivated. People who live overseas, but are not in the military, vote fairly strongly Democratic; and I've seen at least one poll suggesting that even the military folks are pretty peeved at ShrubCo.
As a sidenote, apparently India does a better job at building voter machines than we do: The Bombay Ballot
As another sidenote (edited in later), it's worth noting that Grover Norquist, one of the architects of the modern Republican party's platform, says that the "greatest generation" was, in fact, un-American. No, I'm not kidding: Grover Norquist, en Español. Norquist's real beef with these people is, of course, that they created the "welfare state" -- you know, those awful things like Social Security and Medicare, Aid to Families with Dependent Children, the Earned Income Tax Credit, and so on. It's very important for the good of America that we ensure that most Americans live in grinding poverty and have no influence in government, and that only virtuous Americans -- i.e. those with the most money (because after all, they wouldn't be rich if they hadn't worked for their money, right?) -- control the levers of power.