I think recruiters are bad about running ghost ads, so that they maintain a database of people who are looking.
I can see where a company might do that to get a feel for the labor market. A tight market could lead to higher raises. And an oversupply of labor could lead to none.
And of course the ad company themselves might run fake ads for many of the same reasons that twitter and facebook have fake bots.
I've long suspected this also is common practice for lower-paying jobs with a high turnover rate. They keep their job ads posted so that they always have ready applicants whenever an employee inevitably quits.