There are two aspects to this.
First, it is important to convey a realistic recruitment message. If a firm does not accurately present the job for which it is recruiting, it will have problems. The people it hires may not be right for the job or they might not think the job is right for them. The firm then is either stuck with a bad employee or has to start recruiting again when the employee leaves.
Second, it is important to convey the message in a way that applicants want to hear. If the message is not conveyed in an agreeable way, the firm will not get as many applicants as it should. In such a case, the firm will not be as likely to get the best possible employees.
The advantage, then, is that a firm will get and keep better employees if it does this.