Some games we finished might be borrowed, or have been sold, they might not in the collection list. And even they are in the collection list, it also good to track which game I have finished.
With a finished game list, also easy to generate an unfinished game list, which is the the collection set minus the finished set, so we can have an idea that these games are the ones we need to pick up and play.
And thanks for the great website, I like it, great job!