ACY is going to mostly pull from PHL traffic, and from EWR traffic to a lesser extent. CO won't fly there for the same reason that they don't fly to TTN. Based on where they'd be going (CLE and IAH as a VERY remote possibility) they figure their pax are more likely to go via EWR or just deal with the connection that they'll have out of PHL anyways. For the folks who who raather fly out of ACY than EWR, PHL is the other option that CO makes available. I doubt that CO is losing all that much business by not having service there.