Those coins have reason for not trying to have their coins listed yet.
They are afraid of the bearish market which may bring the coin value all the way down.
But no, the market is not weakening, its coming back in fact. We will witness the bull run very soon.
This is an interesting perspective, in one hand the developers want their coins to be listed in an exchange since that gives the coin some kind of notoriety and it is in a way seal of approval, but at the same time with the market as it is right now most coins will go down in value after they are listed in an exchange and they do not want that.
So they are trapped and they have nowhere to run and the developers of each coin needs to decide how are they going to deal with the situation, but if in fact they are trying to develop a good project the they need to push to being listen in an exchange even if the price of the coin goes down since there have been some projects that went down to almost zero and then the project became successful.