I can think of a third reason for SpaceX to agree, and with great eagerness:

The success of commercial space is in some doubt, right now. For years, there have been doubters who have criticized the effort and predicted failure. All of the newcomers to commercial space need to prove that their out-of-the-box thinking produces results no worse than the old-style thinking that has kept access to space expensive, dangerous, and difficult.

The best result for this version of commercial space is for the survival and success of every company in this new niche of the industry, despite the competition that results. Success builds on success, because confidence is created.

Even before the two accidents, confidence was hard to come by. Even we enthusiasts have been said to have blind faith and irrational exuberance in this new way of thinking.

Although I honestly don’t think that all of the current companies will survive (just as Kistler, unfortunately, failed), I root for them all, especially Bigelow, as that company is the only one, so far, that provides a potential for the rapid expansion of destinations for manned commercial space companies. If Bigelow survives, I suspect that all four of the current top runners for commercial manned launches can also survive and thrive, and maybe leave room for still more competitors.

The result of many successful competitive companies will be the reduction of cost in reaching space. With luck, they can also reduce the difficulty and danger involved, too.

I hope to see the day when space travel is relatively inexpensive and relatively safe as air travel was in the 1950s. There were a large number of airlines competing and figuring out how to safely and inexpensively fly people and cargo. There were many costly lessons to learn, but we were on our way to an unstoppable industry.

Sorry, my comment above came under the wrong subject.
I think it is great that private companies cooperate and specialize on different niches.