Sure, most VR hardware options may technically be peripherals for PCs, but at a cost of several hundred dollars or more, it isn't in the same category as PC mouses or joysticks. The way I see it, VR hardware is essentially a standalone device that connects to PCs, simply so that many people won't need to buy that too, saving them $1k-2k.
Creating exclusive games and buying exclusive content licensing/distribution rights for any gaming platform, especially ones in stiff competition for early adopters and the lion's share of a new market, is a great business decision. If Oculus hadn't secured exclusive content, people would have simply bought whichever hardware worked better, or shipped first. In this case, most people would have likely bought the Vive. Oculus knew that superior content is the tie-breaker and can even overshadow slight technological shortcomings, if they exist.
Oculus should never have reversed their plans to keep the content exclusive. Now, many people will just buy Vives and use them to play Oculus-subsidized content. Oculus could have created a great monopoly. Now I suspect they will have serious difficulty building a sustainable business. Peter Thiel is on Facebook's board and Marc Andreessen is on both Facebook's and Oculus's board. I can't imagine either one would support reversing the decision to make exclusive content.