User blog comment:Tommy,Klaus&Kol2012+/A theory about the empty guardian/@comment-3045936-20181213215633/@comment-10889355-20181213224146

Because John is an abusive dick of a father and he made Sam and Dean’s childhood a living hell that they carried for over a decade.

There might be a time travel in the 300th episode so maybe that’s the only time we’ll see John.