Define "low"! Coinmarketcap lists Nxt's volume as 9th in rank... higher than Peercoin, Namecoin, Counterparty, Mastercoin, and countless others.

Bitcoin amounts to 84% of all crypto trading volume; Litecoin is next at less than 8%; and EVERYONE else is under 1%.

Personally, I think the low volume is due to the exchanges on which Nxt is listed.  We are not on BTC-e, Mintpal, Bitfinex, Bittrex, or Kraken.  And the reason we are not on those exchanges is because the Nxt software cannot -- like any other QT-wallet altcoin -- be added with a few minutes of work.  Exchanges like Vault of Satoshi have said they'll implement Nxt, and have balked after realizing it's not just another alt.

One of the most key developments in Nxt which is NOT getting enough attention is the "adaptor" for the Bitcoin API: a piece of software that translates Nxt's interface to one that looks more like those used by Bitcoin and other alts.  Once this work is complete, all of the high-volume exchanges that have been ignoring Nxt will have an opportunity to implement it more easily.

Progress on the "Bitcoin adaptor" can be followed here: https://nxtforum.org/general/adaptor-for-legacy-bitcoin-protocols