My experience, as someone who has advocated for hiring people along the same lines, is that this is a pitch that everyone will agree is a good idea. But then when it comes time to actually hire someone under it, people will hem and haw about whether or not they have the capacity to mentor people like this.
Usually it then won't happen unless they fit a very specific "comfortable" mold of person that they believe can be a "self-starter" which usually just means someone who's similar to person/people deciding on the hiring in various ways.
Where I work mentoring a junior person is almost mandatory once you reach a certain level. I've been told flat out one reason I was passed for a promotion was I wasn't mentoring people, event though my department didn't have any juniors in at the time, it still held me back (and my boss also started looking for opportunities to mentor outside the department, but I left before that got anywhere for other reasons)
Usually it then won't happen unless they fit a very specific "comfortable" mold of person that they believe can be a "self-starter" which usually just means someone who's similar to person/people deciding on the hiring in various ways.