Probably because the people you hear doom-saying the VR, such as the ones plastered over the Escapist Forums, are only a tiny, vocal, minority of people who are interested in the product. Most people don't think of Facebook as some sort of grim reaper, killing off anything it so much as touches. Some people just view it as another company, whose main service is a large social media website. Most people, when hearing this news, don't think, "DEATH OF VIRTUAL REALITY, RIP OCULUS, WHAT HAST THOU DONETH TO THINE SELF!!!" Instead they think something more along the lines of, "Oh, cool, now they'll have enough funding and exposure to make the best product they want."