Lots of job listings are fake. The benefits to posting fake ones are too tempting for companies to ignore. It provides essentially free data including current salary expectations, market saturation, career history, and much more. This makes it much easier to pay below market salaries.
Let's say you have stocks in your company. In a time span of a week, you suddenly release a couple hundred job postings. Investors will see that as an indicator of massive growth and your stocks will go up.