Given that companies have perfect freedom to publish the salary information, and yet most choose not to, it probably benefits them somehow.
Some people simply underestimate their market value, and companies are happy to keep them in dark, sometimes for years. Other people don't have unlimited time to do job interviews, so if they find something that seems okay and the provided salary is maybe 90% of what they originally wanted, they may choose to take it anyway. If they don't, the interview was a wasted time -- both for them and for the company, but because the company had the option to choose otherwise and decided not to, it's probably a net win for the company.
I have no idea about specific numbers, but if the company spends 2× as much time interviewing in return to saving 10% of salary costs, it may be worth it. If the employee wants to spend 2× much time interviewing in return to getting 10% higher salary, they will probably quickly run out of vacation days. The process is usually asymmetrical; the company spends 1 hour interviewing the candidate, the candidate spends some time preparing for the interview, traveling there and back... also, if the interview is in the middle of working time (it usually is), for the company that's 1 hour lost, for the candidate it is 1/2 day off.
Some people simply underestimate their market value, and companies are happy to keep them in dark, sometimes for years. Other people don't have unlimited time to do job interviews, so if they find something that seems okay and the provided salary is maybe 90% of what they originally wanted, they may choose to take it anyway. If they don't, the interview was a wasted time -- both for them and for the company, but because the company had the option to choose otherwise and decided not to, it's probably a net win for the company.
I have no idea about specific numbers, but if the company spends 2× as much time interviewing in return to saving 10% of salary costs, it may be worth it. If the employee wants to spend 2× much time interviewing in return to getting 10% higher salary, they will probably quickly run out of vacation days. The process is usually asymmetrical; the company spends 1 hour interviewing the candidate, the candidate spends some time preparing for the interview, traveling there and back... also, if the interview is in the middle of working time (it usually is), for the company that's 1 hour lost, for the candidate it is 1/2 day off.