Hulu has just snagged Fox Animation exclusivity; all seasons of American Dad, Futurama, Bob's Burgers and Cleveland Show will only be available on Hulu.
Same thing is porbably happening with DC shows too, WB is a partial owner of Hulu and most of CN shows were transferred to Hulu after they expired on Netflix. Hulu and WB has multiple year CN exclusivity with WB, maybe they could appear on Hulu. I know Amazon has the classic Batman and Superman series.