In good old days, there used to be DC++. Currently I use what is touted as the best client for it AirDC++. Why can't peer to peer file sharing like Direct Conn

In good old days, there used to be DC++. Currently I use what is touted as the best client for it AirDC++. Why can't peer to peer file sharing like Direct Connect be used for such purposes? People have successfully used i2p, torrents, emule,etc.? Can they be tracked and shut down?