They just don't want anymore "why doesn't this support retina display!?!" or "99c?, should be free..." reviews.
If you don't have the app then you can't write a review about it! Isn't this logical? It won't work even if you try again later unless you buy the app.
No my problem was i purchesed a rpg called queens crown. in the app there is a quest which if you ratethe application 5 stars you get 5000 gold! when i tryed it says i need to purchese the app before reviewing. although currently it seems fixed)) most of the messages i got said "please rate this purle software" and "click to rate" teah the purple software one i was like... is my ipod smokin something i don't know about?