I don't think many orgs learn all that much from coaching their juniors, at least after first few.

Juniors are just... necessary in the balance, have to little of them and the mid and senior devs will get more and more expensive, so you hire a bunch of juniors, they get trained on job, and it balances it out.

Hell, if company does it right they might underpay junior-turned-senior for decade before they notice and look how industry pay looks like!