Because a few developers will choose to place ads inside their apps? There will soon be cross-platform ad plugins like this in PCVR software, too. The only rea

Because a few developers will choose to place ads inside their apps? There will soon be cross-platform ad plugins like this in PCVR software, too. The only reason you don't see it more already is that advertisers haven't figured out how to value what exactly they'd be buying; There's so many more factors regarding visibility/readability/placement in a 3D virtual environment, and there's a big difference between a real-life billboard that moves slowly past every driver on the interstate vs a canvas in a VR game where players might teleport right by in a hurry. Even with Facebook solving the technical aspects of measuring impressions/"engagement" in virtual worlds, I don't think the platform will attract many advertisers outside of the gaming/VR industry itself.