I don't think that's how it works.
There's a place for knowledge and experience, and there's a place for fresh talent and creativity.
Also, they have a different value for the company. Experienced guys are worth more, so they are paid more. Younger ones will maybe make it up in volume or not, so they are paid less.
I don't see that as a problem, just reality.
I don't think companies want younger guys because they are cheaper, they are aware they are less productive, esp in the long run, so it's the same deal for them to hire an experienced guy for 120k vs one or two young guys for 70k each (just an example, I don't live in the US).
But... two things...
One of them, inexperienced devs _may_ have a hidden cost in the long run, but for public companies there is no long run, there's only next quarter, and the managers kpi related bonuses. So, costs you won't look at, they don't exist.
The second one, inexperienced guys are inexperienced, so you can get away with paying a lot less than _their_ already lower worth. Also, they will work extra hours for free, will study stuff in their time, not company time. They will travel for free, so as to know new places. They will ask for less money out of lack of experience, and because they value other stuff like getting experience and contacts.
This means that you have to pay an older guy his worth, and you get younger guys at a discount on their already lower value, with no extra cost. Maybe mentoring kids into asking for that they are worth will make them better negotiators, and a little less desirable?