It's not automatic for one very good reason: Sometimes (although not so often recently) this site goes down, or the software is upgraded and people cannot make moves. Admin can then delay the timing out procedure to take account of downtime. Something that couldn't happen if the process was automatic.
Of course, that doesn't excuse the fact, that in the absense of unforseen problems, the 2 day timeout rule should still apply. It's not only fair to both players but to everyone else in the tournament as well.
Yoohoo, Chris or Russ, you still there?