It is to protect it all from graffiti, that's right. As soon as they get a bit built it gets tagged, so they cover it up.
Which leads me to the question. Will they just leave the plastic up forever or once they get finished they don't really care if it gets tagged?
I will admit that the building of these walls does make me feel a bit like a hamster in a habitrail.
Today's bumper sticker: Remember who you always wanted to be