Creators of such sites (including me) tend to focus too much on the number of torrents, no matter if they are active or dead. Regular users are interested mainly in active torrents.
Plus they want to see the current number of seeders/leechers, which is very difficult to keep up-to-date for a large database.
Plus they want to see a torrent creation/upload date, which you cannot get from DHT (you can record the day you found a torrent, but it will work only for newer torrents, not for historical ones).