Some conferences and journals do employ "double blind" reviewing. Whether it is superior or not can be debated. Whether it is actually "needed" or not can also be debated.
But, single blind is just a tradition that makes some things easier on authors and editors. Double blind reviewing normally requires that a special version of a paper be presented for review, since the authors often refer internally to their own work and often use personal pronouns, such as "we". This makes it easy to disambiguate authors unless care is taken. There have been questions on this site about preparing such specialized version to avoid referring to essential early work by the same authors.
Double blind review also can narrow the set of acceptable reviewers. Often enough, a reviewer is chosen because their own work is mentioned in the paper, making it more likely that the reviewer will actually know of the work before being offered the paper for review. While some conflicts of interest can occur, these are normally pretty rare and can be handled via communication of rules for reviewers.
So, if an editor or conference committee agrees that there is little to be gained by double blind review and wants to avoid extra steps, they will likely just follow the traditional practice.