My experience has been that many manager want to run or at least pretend to run a tight ship. So, they would rather splurge on finding that awesome-senior-dev than train people from scratch.
Though this seems odd, it tends to give hiring managers some sense of security when they report to their superiors. They'd rather say:
I have X who has Y years of experience in Z framework
than
I have X who has zero experience in Z and we are going to train them.
It is like Kanehman's certainty effect. They'd rather be certain of competence than bet on the fact that you might be trained to be competent.
Though this seems odd, it tends to give hiring managers some sense of security when they report to their superiors. They'd rather say:
I have X who has Y years of experience in Z framework
than
I have X who has zero experience in Z and we are going to train them.
It is like Kanehman's certainty effect. They'd rather be certain of competence than bet on the fact that you might be trained to be competent.