[the8472]

Torrents don't work well with mobile devices, multicast could be implemented more efficiently at the physical layer of a shared medium. Torrents also have higher latency and you're at the mercy of the aggregate upload bandwidth of the swarm. On a good day they can be good enough for VoD style streaming but that's far from assured unless the distributor at least keeps some backup bandwidth ready if demand exceeds supply (which sounds a bit like a CDN). For realtime streaming IP-multicast would still be the ideal solution.

[namibj]

Well, https://www.bittorrent.org/beps/bep_0014.html isn't even that new, and yeah, it's only for service discovery right now, but I'm pretty sure you'd get multicast support in the popular clients, at least for Merkle-Tree (BEP-0030) torrents with e.g. 2^10 piece size.

[the8472]

BEP14 is totally irrelevant to the discussion here. It's only for finding peers in a local lan, not for distributing payload via multicast. The latter is and always has been via unicast.