Why do legislators try to stifle strong widespread encryption? There must be either legitimate unsolved concerns (like law enforcement) or they're answering to

Why do legislators try to stifle strong widespread encryption? There must be either legitimate unsolved concerns (like law enforcement) or they're answering to other stakeholders who have an interest in weak encryption (big business?). I'd be interested to discover the motivation behind these bills, if it seems that these laws aren't in the public's best interest.