Some are that way I suppose but as I was learning, many far more experienced, late-career gurus went out of their way to teach me. It does require asking good questions and showing some genuine interest and engagement in learning though. It's also important to be able to show at least some aptitude which helps convince someone to invest the time in you.
Over several decades and lots of hands-on experience, I eventually advanced to proven veteran status myself and I was pretty much constantly trying to teach the newer recruits the deeper work of not just how to do it but why and how to think about the overall process. I think I managed to do some good since several of the newbies I informally mentored have now become senior vets themselves. However, several times I was actually told by the division head to spend less time explaining to my staff and just do the work myself as quickly as possible.
Even though I'm now happily retired, I regularly volunteer as a guest lecturer at several university programs. Like many fields, full-time professors don't really have the breadth of practical experience or real-world skills themselves. The good ones realize this and rely on people like me who've successfully done it over decades to fill in the gaps.