I personally think the game would be far better if the old accounts were not held active in the game so long so they could mess with accounts being played by actual players, it skews the game out of true. But the owners of the game run a commercial enterprise that wants more money so I doubt that will change.
I think that's a little harsh on innogames frankly (and by no means an innogames fanboy, just calling it as I see it).
From what I see with rules like banning u/n & passwords being passed between players and many having been banned for it, they're doing as much as is practical to stop or at least discourage this.
What you need to keep in mind as well is that for them to police this any more effectively would mean putting a disproportionate amount of resources in doing so, which is ultimately going to represent a greater cost overhead which would probably be passed onto us the customers in some form (potentially more advertising, more expensive pp, etc).