The point of Unicom is to help announce intentions to others around you, aiding in communication and conflict prevention.
This would be helpful in announcing the intention of moving without jumping straight to taxi, especially given once pushed back we now must start engines and have a longer runup to being taxi-ready.
Even though in real life very few to no airports would have pushback-capable aircraft doing so on Unicom, Infinite Flight’s situation of having Unicom at large airports when ATC is not present justifies this addition.
Perhaps @Tyler_Shelton could provide insight, but I can’t imagine adding an ATC command is too complicated. The Devs might have resisted based on realism, but see my third point for that. I’m all for this!