I don't see how prostitution would ever be considered a public service.

However, the old testament alludes to the fact that only prostitutes covered their faces.

   “14 And she put her widow's garments off from her, and covered her with a vail, and wrapped herself, and sat in an open place, which is by the way to Timnath; for she saw that Shelah was grown, and she was not given unto him to wife. 15 When Judah saw her, he thought her to be an harlot, because she had covered her face.”          
                                                  (Genesis 38:14-15)