That question has been asked a lot, and for the long answer, here is an excerpt from my interview with Ryan Sanders before the campaign began:
It was a decision based on logistics, production goals and overall simplicity.
First, logistics. Fulfilling a project with six separate pledges takes a lot more time than, say, two. I wanted the games to get out to backers as quickly as possible with minimal mistakes, so combining the six games into two (or three) pledge levels helps to streamline that process. Also, this helps with shipping, both for DHMG and for backers. Putting three games into one package helps reduce shipping costs across the board.
Second, production goals. I want all six games to succeed and be published. If I was to offer the games separately, there might inevitably be one or two games that might garner more pledges than others. Do I then take the pledge totals for those two games and spread them across all six? Is that ultimately fair? I see these games as appealing to a certain group of gamers that enjoy playing compact card games within a certain time frame. We’re offering a variety of games that will appeal to a wide range of gamers, so it just makes sense to group them into thematic packs.
And, third, simplicity. Managing a campaign with six separate games is already a tough job from a production standpoint. By simplifying the pledge structure, Dice Hate Me Games can focus on getting the games out in a timely fashion rather than fretting over the Kickstarter campaign structure.