Well, I think we mostly use it to inherit _gameRef and the constructor.
It probably doesn't *need* to be, but I seem to understand this is how we do it for consistency.

(Or at least how Mnemonic seems to do it all over the place).

Are you suggesting we see if we can do away with it?
If so, I guess we'd better make a separate job out of it and refactor the whole thing, since IIRC it seems to be customary in a number of other places. 

(I may not RC, will check)