User blog comment:Anonnnomoose/TESWiki Guild/@comment-74.4.77.139-20120606023808/@comment-69.48.155.2-20120606151223

What goldenfire said, from personal experience (WoW) a large amount of people will join guilds just to rob as much as they can of value before leaving/deleting there throwaway account. So non trustworthy people are more likely to do this and more reliable people are better for pvp.