It's useless coins, toys for a short time. Poloniex not add to itself coins like this, so as not to create conflict with the law.
You mean coins like POT that are listed on Poloniex? I think most of the pot coins are stressing their intent to partner with and build services for legal dispensaries.
POT are listed on Poloniex a long time ago, when Polo was small exchange with low volume. Now they operate strictly according to US law. I do not think that they would want to spoil their reputation for the sake of adding another fork without future.