Ask HN: Why are all companies using hiring websites

Every company seems to be either using greenhouse [1] or lever. Why is it not intuitive to get your application through your own website. What's special about this companies. I even expected read.cv [2] to use their own database. Why cant we accept jobs through our own platforms? [2]https://read.cv/open-roles https://boards.greenhouse.io/supabase/jobs/4776924004