With a very few exceptions (I can think of one anonymous early adopter with a pretty big account that suddenly disappeared and no one ever heard from; we suspect he or she may have died) the abandoned accounts have almost no stake and don't matter. Apart from those odd cases like sudden death people aren't in the habit of abandoning large holdings. If leaving most will at least power down, and certainly many did.

A lot of those million accounts never voted for witnesses either. New users who signed up looked around for a bit and then left.