In TCG Pocket, Druddigon's pretty much the go-to wall. He's got a decent amount of HP, but his real advantage is that he has an ability that lets him deal 20 damage to anyone who deals damage to him.
However, Cubone in TCG Pocket has one 'attack', to growl at the opponent and reduce the damage of their next attack. The problem is that druddigon generally doesn't attack - most players don't even have the energy for it in the deck, just using it's ability to chip at any opponents who try to push through it.
So what is Cubone doing?
His best. Cubone is doing his best.