My point is that if juniors aren't getting hired they never evolve to become seniors.

As long as they keep to the tall grass and avoid staff predators they should be OK.

Since you seem to like metaphors maybe this helps you understand my point: If they stop fertilizing there won't be any grass to harvest.

To make myself even clearer: They're (and you I guess) assuming other companies will hire and train the juniors for them, but it's short-sighted. If everyone did it how are they going to learn?