That's at least partly because Facebook hasn't had much luck with hardware, and it's still unclear what kind of changes Facebook could make to Oculus' Rift virtual reality headset, according to Sherri Smith, senior staff writer at Laptop Mag and Tom's Guide.
The HTC ChaCha and HTC First phones, which were released in 2011 and 2013, respectively, had Facebook buttons built into their hardware, but both phones were flops, Smith said.
Gamers are concerned that Facebook could make changes to the Oculus experience to make its Rift headset less gamer-friendly, for instance by adding in-game pop-up ads, Smith suggested.
"We're making a long-term bet that immersive, virtual and augmented reality will become a part of people's daily life," said Facebook CEO Mark Zuckerberg in a conference call Tuesday.
Facebook shares were down more than 5 percent in afternoon trading Wednesday.