Which would you pick? The VR headset with 10 multiplatform games or the VR headset with 10 multiplatform games and awesome 3 exclusive games?
Which would you pick? A console that has every multiplatform game or a PlayStation with support 16 first party studios and every multiplatform game?
What I mean is that Oculus or facebook aren't interested in driving the adoption of PC unlike hardware manufacturers. Therefore an exclusive serves no purpose. If Oculus buys exclusives for their VR, they will essentially be risking entering a war with Valve/HTC who may end up doing the same. They don't want other games to not be on their platform due to another PC VR device's exclusive arrangements, especially when Oculus will rely so heavily on valve due to Steam.