Some rabbits are more inclined to binky than others. Doesn't necessarily mean a rabbit isn't perfectly happy if they aren't doing it. I have one rabbit that doesn't binky at all, but buzzes when he is excited about his food. I have another that doesn't binky when let out in a new area, but will instead do bunny 500's zipping around super fast. So all rabbits are different.
Though when the binkying does happen, I've found it most often occurs when a rabbit is super excited, like when they first get let out into a new area to explore or when they are being let out after being penned up. They can act a little tentative at first, but once they are sure they are safe the binkies usually start. But then once a rabbit has explored and is completely used to an area, the binkies die down and may not happen again until they have something to get excited about.
