Bet my bottom dollar that DC doesn't want the embarrassing humiliation of people who haven't seen that show to do so, lol.
Then I guess they better spend some of those DARK KNIGHT millions buying every copy of the 1966 BATMAN movie which is available on DVD.
Even if they bought every copy available, the rights to that one are still in the clear. They can't bury it the way George Lucas has tried to bury the Star Wars
As for protecting new viewers from cheesy Bat-products, that doesn't make sense. They still sell copies of Batman & Robin,