The first reason is that unlike NCS, you don't need a laptop, wired interface and technical expertise to code your car with Carly. NCS is factory software, so of course it has more coding possibilities (yet less than can be achieved using PA Soft ), but you really need to know what you are doing with NCS - it is not just a matter of choosing options in plain English, you need to know the particular module where the coding information is stored as well as what coding alternatives are available for the command you are working on. For example, I coded the legal disclaimer for the Nav on my E70 not to display (a fairly simple job).
The procedure was to connect NCS to the car, read the car, then select the appropriate module (in this case the CAS) and read the data from that module. From there it is a matter of opening the file read from the CAS, modifying the command (in this case from LEGAL_DISCL aktiv to nicht_aktiv, saving the modified file, then using a custom NCS profile to write the data back to the car. All up, about 15 minutes (I am not a novice with NCS).
I coded the triple flash indicators on the same car using Carly in around 30 seconds.
Although there is plenty of info on NCS, there is no factory backup and there are plenty of users who have wound up causing problems for themselves by changing data that should have been left alone.
Yes, Carly can code all doors to unlock when the ignition is turned off - you can read about exactly what coding options are available here Code BMW - What is possible with Carly for BMW