Why do I have to know the user's group to assign them?

I think it's really annoying to have to know the group of an agent to assign them a ticket.  I should be able to simply start typing the agents name and be presented with a list of the groups for that agent and allowed to pick one.  If I don't know the group, I have to select each group in turn, then search for the user, then move on to the next group.