Many government contractors currently provide NO sick leave to their employees, who work in government offices alongside federal government employees who do have sick leave benefits. Requiring contractors to provide sick leave to their employees would set an appropriate example nationwide for employers to provide their employees with sick leave annually, which would provide for a healthy workplace by encouraging sick employees to stay home, recuperate, and not spread their illness.
Moreover, it has been shown that paid sick leave policies strengthen worker loyalty, increase productivity, and reduce turnover.
See http://www.americanprogress.org/issues/labor/news/2012/11/16/45152/myth-... for more information.