Firstly, the Recycle Bin, by default, is only set to hold 10% of the capacity of your HDD. If the Recycle Bin runs out of space, it will permanently clear files to make more space for new "deleted" files.
Secondly, when something is "permanently deleted", instead of actually clearing the bytes on your Hard Drive, the system simply modifies the Master File Table to mark the bytes as clear, but leaves the data sitting on the HDD. That's why files are recoverable. At some point later when you start trying to add new files, however, Windows will overwrite old empty blocks with the new data.
Windows doesn't just overwrite files that exist. At some point you uninstalled or deleted the application files, and you've since installed new games which have filled in the space.