We don't collectively contribute to save shareholders. When a bank goes under the depositors are made whole through government insurance programs. Shareholders get nothing.

In 2008 I believe bailouts did go to companies to keep them afloat (and thus helped shareholders). However, TARP returned a small profit for the government, so it didn't end up being a gift of free money overall imo. (reasonable people can say that the bailouts were excessive and introduced moral hazard for sure).