No OB on US courses? Played in a condo canyon lately?
Things like roads and OB as hazards are underused as primary hazards, because they really aren't practical as crowds on and around the golf courses grew. And, oh yeah, the lawyer population.
Plus, in pure golf terms, just as water is often too penal for a particular shot, so is OB, esp. if there is potential for damage to property and life, besides the penalty stroke! Some recoverable hazard often makes more sense in terms of encouraging bold play. OB probably discourages bold play in most players.
Given how little most golfers like it, I think its probably used more than enough.