It's to try and cut down on spoilers, though even with the classified system, there are still several spoilerific things you could figure out or theorise about by looking at the data. I like to know as much as I can about something beforehand (especially if it involves doing a little digging), but the next Destiny player might prefer to be surprised and not know what's coming and you have to respect that. As for why Year 2 versions of Year 1 weapons are getting classified, they were probably missed because alot of the armour had been in the database before the last update. Typically this will get fixed at the start of each week, and new items get declassified a week after they get discovered. If you have an app, I would just setup a lock state that prevents you from interacting with classified items because they probably won't be going away anytime soon.