1) Why pay someone to learn? In both terms of money and other devs time being sunk into helping you learn.
2) If you do know "tool X" and its a primary tool then its a lot easier to quickly evaluate whether or not standards will align.
Personally I don't mind hiring Jr Developers that cost less, are mold-able, and are willing to put in extra effort. Could any experienced dev lean it? Sure... but its more costly and often ends up in a "I have now studied X for Y weeks, we do X wrong I refuse to do X your way."
I would say that one of the most important qualities a developer can have is the ability to learn.
Perhaps, you expect all the learning to be done outside of work?
I never claimed learning is not important, if anything I supported that in my comment in hiring eager jr's.
My point being is if I am hiring someone "experienced" I need someone who can mentor others, own projects, and help drive our current products forward. If that person will need to come in and learn the job... I might as well hire a JR and train them up instead or hold our the X months the "experienced" person will need to learn to bypass that whole ordeal.
Usually when a job candidate is not selected they aren't given any information about why.