When it comes to job listings, wages are often deliberately omitted. Mandating that they be listed would empower job seekers by giving them the information they need to avoid working on applications that will not provide the income they need to sustain themselves. Many applicants ask that they no longer be considered after learning the wage, which wastes the time of both the applicant and the human resources staff.
If the wages are based on experience or negotiable, it would be acceptable to include a salary or hourly wage range that the hiring party would be willing to consider.