If you attach the suppressor to your barrel (with the direct thread adapter installed), when you go to remove the suppressor, the direct thread adapter will unscrew from your suppressor before it unscrews from the barrel. You could eliminate the issue by gluing the adapter to your can or mechanically locking it to the can somehow, or just never removing the suppressor again.
Like others, I went the DT adapter route and ended up having to use pliers to remove it from the barrel after it would unscrew from the suppressor.
Imagine having to use pliers to get your direct thread adapter off of your barrel when it's ~6" deep in your handguard. But like I said above, you could just leave the DT adapter on your barrel as a muzzle device.