There is a problem with share buybacks—but it isn’t the one many critics and legislators are obsessed with.

Some critics claim that repurchases starve firms of capital they could invest for the long term, harming workers to enrich shareholders. Democratic Sens. Chuck Schumer of New York and Tammy Baldwin of Wisconsin agree and have introduced legislation to “rein in” corporate stock buybacks. The bill would give the Securities and Exchange Commission authority to reject buybacks that, in its judgment, hurt workers. It also...