Nickname REQUIRED??

I have to go in and add first and last names to all my users (I imported them from another CMS, and it did not take that info. When I’m adding the names, I noticed it says “Nickname (Required)” on all their profiles… I have to do this to 1100 profiles, so I don’t want to have to come back and add a nickname later. Is this REALLY necessary? It seems to be saving fine after I put just their first and last names. Why does it say (Required)?

Thanks!