As promised when the hardware was made official, Google delivered well over 50 Daydream VR apps by the end of 2016. Each of these apps were from quality, hand-picked developers, quickly creating an environment of much higher quality than you'd experience shopping for Google Cardboard apps. Volume is still an important thing to achieve, especially when there are developers out there with VR ideas the people at Google haven't even considered yet.
With more people scooping up Daydream View headsets at the discounted price, Google has shifted focus from quality to quantity by publicly guiding developers on how to publish Daydream apps. See at Google
Until recently, the only way to get an app into the Daydream part of the Play Store was to work directly with Google. You could still publish a Daydream app to the Play Store, in fact several have, but in order for that app to be seen by people browsing for apps while wearing the headset that partnership was necessary. That arrangement has now changed, replaced with opt-in instructions for getting your app published where Daydreamers can see it.
What does this opt-in mean for developers? For starters, it means the app must meet all of Google's quality criteria for head tracking and the ability to read text without squinting.
Developers also need to ensure their app icon is properly formatted, and a photosphere from inside the game people are about to play needs to be provided so it looks nice everywhere. As long as developers follow these relatively simple rules, their app is added to the Daydream app as an option for download.
This is an exciting change for several reasons. First, it allows Cardboard developers to more easily port their apps to Daydream and include Daydream Controller support. Second, app categories Google hasn't been supporting will quickly become filled with more compelling options that better compete with what you'll find on Samsung's Gear VR.
Finally, and perhaps most important, this change means Google is ready to see Daydream grow at a pace it can't maintain by individually vetting each app before it is published.