Unexpected Rough Air

This might just be a Delta thing. I wouldn't know what the other airlines do. During their all-important flight safety demonstration (for any aborigines who might be on board), they encourage seat belt use at all times while seated, "in case we experience unexpected rough air." Rough air? They used to say turbulence. Is this just a case of dumbing things down? There's no way a word change like this occurred without internal memos, meetings, discussions, re-training, etc., etc., so it must have some purpose.