As the other commenter mentioned, they dont support port forwarding which kills torrenting ratios. Share ratios are extremely important for private trackers, which is where almost all the value in torrents are.
Its _much_ more straigtforward to get a couple usenet indexers, hook up a VPN (or dont even bother since its over SSL anyways), and call it a day with full internet bandwidth available and no fuss about share ratios.