The reason to hide previous ratings is to solve the problem that you can see where a player is going to end up, without spending on ADV, if you can see that player's ratings history. However, there's a simple new way to game the system; copy and paste all ratings into an excel spreadsheet, once per season.
Since Mike called that "insane," I'll let you know that it took me all of 12 minutes to copy and paste all current ratings for all players for the world that I commish into an excel spreadsheet. 12 minutes per season is a nothing time investment to obtain the sizable trading advantage to owners who do this copy and paste task. Even worse, owners who are new to a world have not had the opportunity to copy and paste (or use their memory), placing them at a serious disadvantage in trades.
It's silly to make a tedious task yield an important advantage. Ergo, hiding previous ratings is a bad idea; it solves the problem it's trying to solve only for people who don't have 12 minutes per world per season or who are new to a world.
As damag points out, the real solution to the 0 ADV problem, which will work with or without hiding previous ratings, is changing player development and recovery patterns. I await that eagerly.
For what it's worth, in the world I commish, I'm making those seasonal ratings downloads publicly available.