Our culture is obsessed with risk reduction, to the point of an "at any cost" attitude about it, and we very seldom stop to look at the real facts about the risk we're reducing. Heck, there was a thread on the theme parks board a few days ago about taking an 11yo boy into the ladies room for fear something would happen to him using the men's room or waiting for his mother outside.
According to the NHTSA only 19% of children that should be in a booster seat actually use one. Still, for 2009 - the most recent stats I have on hand - car accidents accounted for fewer than 400 deaths of 5-9yos (nearly all of whom should be in boosters) and fewer than 500 of 10-14yos (the age group under discussion by many of us who "sacrifice safety" due to social/peer concerns). Boosters reduce risk, but at the older/bigger end of the recommended age/weight/height range it is a small reduction, not the huge difference you see in the statistics for babies and toddlers.