Voxels isn't even a coin, just counterparty or omni token spam. I don't remember which.

Decred is a pretty decent project, in the sense that a lot of work went into it, and it is trying to do interesting things with refined PoS+PoW hybrid, voting, etc. I don't see any reason that shouldn't be listed.

For a while Poloniex seemed to lay off listing every piece of shit, but they seem back on that game. Maybe it has something to do with the topic of this thread; they fear the end of the ETH windfall and need to get back to their core business of listing garbage.