The normal use for VNC is to enable someone else (IT support?) to control your PC. Since your IT support seemed well acquainted with it, it isn't so surprising that it's installed on your PC then is it.
And since you realised how it might enable you to monitor juniors - it's not a huge step to imagine someone might want to at least have the facility to monitor you, I would have thought.
Though in all likelihood, IMO it sounds like it's simply an "IT thing" to have it available if needed.