Because the Oculus headset works on Steam games, but the Vive doesn't out of the box work with Oculus Home. You can make it work, but it's not quite official. The Rift is also a little bit more comfortable and people seem to the think the display is generally better.
The real reason not to buy the Oculus is because there aren't motion tracked controllers for it yet. There also isn't a lot of room scale experience out there with Oculus so it's not totally clear how it's going to compare when the touch controllers are available.
Early reports sound positive, but early reports are early. The potential for the Rift seems a little greater. Oculus Touch controllers look like they are going to be a real nice piece of kit.
Disclaimer. I went with the Rift because it was more comfortable and I had no problem waiting for motion tracked controllers.
The real reason not to buy the Oculus is because there aren't motion tracked controllers for it yet. There also isn't a lot of room scale experience out there with Oculus so it's not totally clear how it's going to compare when the touch controllers are available.
Early reports sound positive, but early reports are early. The potential for the Rift seems a little greater. Oculus Touch controllers look like they are going to be a real nice piece of kit.
Disclaimer. I went with the Rift because it was more comfortable and I had no problem waiting for motion tracked controllers.