There's already too many applicants for every job opening. If you make the process even more automated public job listings/applicants will be sidelined entirely.
My team hired a jr dev a few months ago. The posting got several thousand responses on LinkedIn alone. We noped out of wading through all of those and just went the referral route.
It's busy work to justify a lot of positions. Think how many people are needed even for a minor change like that in an organization as large and bloated as google