Google Play now has quite a few opt-in features for apps. You can join a beta program, add apps to your wishlist, register to get notifications when apps/games are released, and so on. If you want to wipe all of these settings at once, now you can.
A new 'Google Play preferences' section in the Play settings is now visible for some users (it seems to be a server-side rollout). Inside, you'll find one-tap options to clear your wishlist, leave all beta programs, unregister for all upcoming events, and remove all app/game pre-registrations.
You've always been able to manage these on a per-app basis. For example, the wishlist can be managed by selecting 'Wishlist' in the side menu, and a list of all the beta programs you're enrolled in can be found at My Apps > Beta. The only difference now is that you can wipe all of them in just a few taps.
I think the main use for this will probably be for troubleshooting; if someone is complaining of app crashes, leaving all beta programs could potentially resolve the problem (especially if they are enrolled in the Google or Play Services betas).