People don't join groups that are amorphous blobs in their minds. Putting a human face on union activities is vital to get people to join. Preferably that'd be their own co-workers, people they've already got an established relationship with, but in the absence of that someone to be a figure to just be seen is necessary.

It's a double edged blade though. Hero worship developing is a potential problem as you've said, and in shorter term the faces representing the unions will be marred by MSM as best they can. If the unions can't keep on building goodwill these leaders will be a factor pushing people even after they've gone.