Why would they do this

It makes the company seem productive to attempt to show investors that things are rosy and growth is self-evident

It makes current employees nervous they might be headed for the chopping board of redundancy, so that they might start working harder to safeguard their own job security

It lures in promising candidates in a hoarded talent pool for a later date when a hiring manager might have a real job.

https://thedailybell.com/all-articles/news-analysis/fake-ghost-job-posts/