Employers benefit from professional standards as it keeps employees following good professional ethics and rules.
When starting a new role within a company a contract is given which is read and signed agreeing to certain standards, rules and regulations.
If professional standards were not in place employees would have no rules to follow. For example a call centre advisor could go for their lunch break whenever they pleased and with their friends which will leave less bodies to answer incoming queries driving productivity down. Or perhaps again an employee decided they are having days of or leaving early which will impact an organisations revenue greatly.