The goal of the companies and recruiters is to fill open positions with qualified candidate asap, hence why some would even pay job boards to promote their jobs or offer referral bonus. So my take is that companies would love job boards like this to freely advertise their positions to folks who might not otherwise come across these positions and increase their top of funnels. So in this case, the incentive of aggregators and companies are aligned and it is a win-win situation for both.

I don't know why a company might not want to partake in this, but would be happy to take it down upon their request if they like to make it more difficult for candidates to stump upon their openings.