The best hiring is generally expected to happen through referrals, so there's not a ton of pressure to improve the public application pipeline beyond the minimum required to keep it functional.

One problem with referrals is that referral bonuses tend to encourage referring people they barely know and never really worked with. But actual networking often works.

This is an easily solved problem if you start discounting referrals from employees who refer a lot of people who generally fail your screening interviews.