It seems that companies might have very good reasons to hang on to a video game IP even if they have no intention of using it. I imagined this would mainly be to prevent another company from using the IP, but Michael Cain, a developer on Arcanum, has another reason: taxes!

When Microsoft bought Activision, they had to assign a dollar value to every "dead" IP they acquired—including Arcanum. Let’s say they assigned it a value of $5 million.

If Microsoft decides they will never make Arcanum 2, they can write that $5 million off as a total loss to lower their tax bill.

So that means that if anyone wants to buy the IP, even if Microsoft is never planning on doing something with it, it can still be more valuable to sit on it. It's worth more as a tax-shield than a source of revenue.