When a player in-game links a map it will take you to the page on this website regardless of whether you have the map or not. If a player does already have the map and for some reason forgets that they have it (when you have over 1000 beat-maps it is easy) they will likely just re download it. Not only does this take up the players time (even if they searched for it first it might take several minutes) it uses bandwidth. A solution to this problem would be making links check to see if you have the song first and if you don't THEN taking you to the website to download it.