This question already has an answer here:
There seems to be a lot of users with names like user. Why not impose that they at least give a nick name. Makes it easier to respond to an individual and it would be a minimal effort to do this. Why has this not been done?
I just think that if people set a username that they are more easier to identify and also that they are more interested to have a "more" real presence - just not a fleeting experience and in the future being a more active member of the community.