Considering that Titans was sold to Netflix, this move is interesting. Since then WB was bought by AT&T and a WB streaming service is coming.
Since HBO and DC are owned by WB, this means they are not making a profit on this move, but rather keeping the content in house. This seems to be a move towards strengthening the brand by sacrificing profits.
I think that we'll probably see confirmation of this trend in the near future, with content being pulled from Netflix when the contracts are up and no new content being sold to them outside of the US. The destiny of the international rights of Swamp Thing will probably make this more clear.