A warm welcome to Pet Talk lizelizard,
I hope to see some pictures of your pups.

I am not sure why some dogs play and others don't.
I will assume dogs, like people have their
own distinct personality.
Some dogs are just so laid back.

We had a little terrier many years ago, that
only played while she was in the puppy stage.
Once she matured she acted like an independent old fart. lol