Stackoverflow deprecates OpenID support, a drawback for federated logins

I just received (as you may, too) an email that the famous #StackOverflow Q&A community is dropping #OpenID support, making it impossible for me to use #GNUSocial as login provider. Now they ask for an email address and password to enter.

What sad development, dropping features of a website.
Or use #facebook or #Google to login? Why can they maintain such centralized and proprietary services but not open and decentralized?
Maybe to weak abstraction or missing patterns like facade or adapter?