Some accidents aren't survivable, despite seat belts and air bags. You can tip the odds in your favor with mass, that's why we pay the price (in purchase price and gas) and my wife drives a Suburban as the "Mom taxi". We know several people who were the sole survivors or significantly less injured than others in the same MVA by being belted in their Suburban. It may socially and enviromentally irresponsible in the grand scheme, but it's what I can reasonably do to prospectivly protect my family.