Because we need to make sure that we don't require everything to have admin rights. :)
In terms of user roles/privileges, I am often an admin (Sysop or Bureaucrat) on the wikis for the projects I am organizing conferences for, or I know people who are and are willing to do some setup on my behalf.
This means the privileges of a Sysop are accessible, but it would be good to only need to use them once or twice for setup (perhaps the suggested workflow is to create a namespace for a conference and give the conference organizers admin access only to that namespace?) Generally speaking, "normal users" on a wiki should be able to be conference administrators, I think, since the ability to organize an event is orthogonal to the ability to moderate a wiki, and because some people come in specifically to volunteer for the conference.
I am usually not the sysadmin. Conference organizers usually do not have system administration knowledge (I'm a bit of an exception) so it's going to be important to have installation/setup instructions that they can just point their sysadmin to. The instructions should tell the conference organizers what information they need to give the sysadmin (name of conference, usernames of people who should be able to admin it, etc). so there's not a lot of need for back-and-forth emails.
This post was posted by Mchua~mediawikiwiki, but signed as Mchua.