The answer is money sadly. Even sadder is the fact that there are people who find it acceptable.
I used to hate it when people suggested that Bethesda should hand over the rights of Fallout to Obsidian, but I'm starting to agree with them more and more. They just seem to understand what Fallout is supposed to be far more than Bethesda does at this point.

I love it! I just started the DLC last night and as I was walking alongside Ada, I got side tracked by different locations that I actually never cleared. Then I was thinking, hmm, I should build my Robot workshop and that took all my play time. I converted Red Rocket into my own little hideaway and garage. No settlers will set foot here! 
You better run and hide!!!! Using Zeta in the same sentence as NV DLCs... the horror! *shudders* LOL And I wish to play through NV DLCs over and over and over. It's not about one developer vs the other, it's all about story and the way the game/setting/content makes me feel when I'm playing it.