For what reason is CMC listing NEM like this? Does it matter if the exchange doesn't take Trading Fees?
It does it for all coins with zero fee markets. It regards that volume as less legitimate than exchanges with fees so doesn't count it.
Still, 5 million less is nothing compared to the any of the top 10 in volume. Have a look. 13 million volume is still not much.
Most of those other coins are mined which accounts for a big amount of necessary volume to pay bills. The other non mineable coins like Ripple simply have a much higher profile.