This article makes a number of the standard arguments for hiring juniors and a couple new ones:

- Companies should hire juniors [at their own perceived detriment] to improve the overall industry

- Hire juniors because strong companies are resilient to junior mistakes [rather than hiring seniors and also becoming resilient]

- Juniors learning fast inspires others

- Juniors will teach your seniors how to use AI

Perhaps you can see why most companies don't find these terribly compelling.

Personally, I suspect we're going to have to wait for capitalism to fix this. Senior engineers will age out and the supply will drop. This will increase the cost of seniors until low-cost juniors start to look like a better option to the median hiring manager.