I think the point should be as RonWhisper points out, to encourage different classes of ship to fight in those ships using the tactics they are suited to in order to contribute to a team victory.
I don't think penalising perceived inactivity is the best way to encourage this. I think changing the game economics to reflect best practice for each class is the way forward. I play DD mostly and it is very annoying when you have busted your hump to take caps, spot enemies and take down bigger ships and you have been blown out of the water by the combined fire of what seems like the whole enemy team, then you turn around and there's a friendly cruiser or BB at the back of the map without a scratch and seemingly hiding.
If DDs where better rewarded for taking caps and spotting and cruisers better rewarded for supporting DDs etc. up the classes then the game would feel more realistic and team play would develop organically.