Don't get me wrong, that's a good point, but at the same time they aren't building four or five different types of attack subs, nor are there four or five different kinds of capital ships.
I suppose if you assume that most of the ships on the second list were in service as a result of re-arming at wartime, and are now mostly decommissioned, then it makes more sense. But even so, it's still strange because there isn't a lot of diversity among the ship classes. Norway, Steamrunner, Intrepid, Saber all being very similar ships serving similar purposes and all built around roughly the same time.
It's especially odd when you see the same 2-3 ships over and over from the Romulans, Klingons, Cardassians, Dominion, etc.