I know it feels bad... and it is rough... but the releasing on different platforms is a different concern from making all platforms exactly equal.
It's like, a lot of the comunity would love to be able to play multiplayer games against people on other platforms... even the Devs from LoG would love that... but it is not an easy thing, even though, from the outside they seem 90% of the way there.
Likewise, adding the DLC content would required developing systems outside of the scope of development to make sure people could get the EXTRA content simply and with out complication OUTSIDE of steam/xbox/playstations delivery networks.
It would be great, but it's a lot of development time up front to accommodate a market that may or no pay and, (even if they did,) may not cover the development expense.
This all sounds like a lecture, and that is a bit of a d**k move by me... I'm really sorry.
