Collecting has never quite been an attractive feature to me, so I second what was said by @Hare and @SingSong.
Personally, I am much more intrigued and lean more towards having sites with a battling system that permits looting, which I find much more rewarding than completing collections, especially if it is that type of collecting where you"lock" down the items by submitting them in the collection itself, thus making it impossible to remove them. I've never been much of a display type of person, so it never interested me, perhaps aside from the items which have no use and instead of cluttering my inventory I'd move them to the collection feature.
I am all for having the type of collection to unlock a certain map area, or perhaps even a certain feature, as long as there is an incremental increase in difficulty between obtaining each piece. In my experience, the jump from one to the other is a bit too large in that it makes it conditional for you to rely and adhere to, in lack of a better word, "side activities" in order to even be able to shoot for the next piece. That in itself I suppose is fine, but then the rewards I think should be proportionate which is something that I find to be lacking most times, but then again it really is an equilibrium which is difficult to balance in terms of content updates which would justify the entire bit.