Honestly, I don't have an answer for your question. I'm just eager to hear answers.

Ethan, one of our dogs, sounds alot like Miss Mickie. He came from an abusive home. We've had him for 2(maybe 3?) years now, and I've never seen him truely play. He's picked up a toy everynow and then, but the only time he does it is to keep it away from the other dogs...
I've tried numerous times, and I still try, to get him to play with toys. He doesn't seem amused at all and just lays on his dog bed, trying his best to annoying the pesky human. =D
He would much rather lay around and sleep than to play around.

Who knows? Maybe its because he never learned that it was okay to play when he was little because he was in abusive care. Or it might be because he never had toys to play with when he was a puppy.

Anyhow, I'm eager to hear other views on this subject!