In 8x or less magnification, individual focus binoculars are actually pretty practical for a lot of hunting. They work partly because lower-magnification binoculars have greater depth-of-field than 10x+ binoculars, and because our eyes can also focus a little to accommodate the view. IF binoculars are also very easy to seal against moisture, compared to focus-wheel binoculars.
IF, however, doesn't work as well with more magnification. Plus, bird-watchers buy an awful lot of binoculars, and they're typically glassing at closer distances than hunters, often less than 25 yards down to a few feet. They require quick-focusing, so most binoculars are made with the birding market in mind.
