The program can connect to the daemon and talk to it. (For nodejs, not to imply js is the best choice, just for testing-time, better C/C++) (also know mpd does it)
It being a daemon might make it easier to script with generally, easier to plot/log anything you can query, slicers, viewers, manual control, or the same thing via (something like) Octoprint. It makes things more flexible in terms of how you choose to do things.
Note that you dont have to take this seriously or as neccesarilly your job or anything like that, its like one of those suggestions you let woosh by. I am being a spoiled little brat :p, been using pronterface so far, but now i feel like i should try this one...
Anyway since this is in C++ program, i thought it was a good idea to put the note here. To be specific anyway: