What's a good theory as to why these ones haven't taken off?

Bittorrent got there first.

More that bittorrent was significantly faster and more convenient for users. In general, the more anonymous you want to make a network, the worse the tradeoffs involved will favor performance. Tor, for example, is designed to be low-latency, such that you can actually use instant messaging etc... but if an entity has the ability to monitor enough onion routers simultaneously it is actually trivial to pinpoint the origin of a message. This can be countered with traffic mixing, random delays, fake traffic, etc... all of which significantly increase latency and reduce bandwidth.

Could someone explain to me how these protocols are superior to Bittorrent?

Your definition of "superior" may imply vastly different trade-offs. If you want files fast, then they are quite inferior to Bittorrent. The aforementioned protocols can vary a bit in what they do well, but in general the goal is to protect the identity of participants from hostile peers on the network. With Bittorrent, the goal is to transfer files efficiently with no regard for privacy, and it's very good at it.

It's harder to sue someone transfering a file with these protocols, however it's almost certainly slower to get a file with these protocols.

Then there's the network effect. BitTorrent is more popular, ergo there will be more files available