One option is HR compliance with some kind or procedure.

One other thing I've seen (many times) is to pacify an over-worked team: the team is working crazy over hours, demotivated, asking for help. The manager knows is impossible to hire (head count / budget limits) and so they open a Job Offer, where they can show "we are searching for help, but nobody comes". How do I know? once I was in such over exploited team, so each of the team made a fake resume that was, of course, like a glove for the position. Nobody got a call back. When we confronted the manager, he had to confess. [in case somebody asks himself, 6 months later the whole team was gone]. Then same company, I applied for a job, where my resume was really perfect for the position. As I received the canned response, I called the manager, pressed a little bit, and also said "we had to do as we are searching, but we are really not".

Yet another one I know of, because of reasons: HR consulting companies and also some HR departments want to test if they are paying too much/too little, want to have some "market measurement". They fake jobs, fake interviews, and they would inconspicuously ask "how much are you earning now" and/or "how much do you want to earn" and that is all they want from you really.

Yeah I've heard that angle too. Really nasty. Glad the team wassable to stand up for themselves and walk away from the abuse. Sure wish that could be the outcome more often; it'd fix a lot of things overnight.