Equity in the old GM got wiped out. It's more than a practicality for you if you held shares in the old company -- or your retirement fund held shares.
This is like calling a heart transplant an everyday affair. It's deeply incorrect.
Corporate reorganizations under bankrupcy law do happen, but they are rare, newsworthy, and very disruptive to workers (at a minimum, their pension and health benefits are renegotiated). Shareholders being wiped out is not normal, and retirement funds -- or really, the stock market at all -- would not work if it was.