Like it or not, a unionised legacy workforce is expensive. (Sickies, staff travel, allowances, penalty rates...dry cleaning!) There is a never ending crowd of keen young people willing to do their job for half the $. Their enthusiasm usually burns out after 6-12months, ready for the next batch.
Of course that theory seems to stop at senior management levels when suddenly we need "experience" and "we have to pay market rates to attract the right talent" and people who are made redundant have roles created for them out of thin air.
Reality is the same game could be played with CEO and senior managers if boards wanted to get serious. The issue however is that once you get into senior levels of any corporation it tends to be a bit of a closed shop and very much on who your mates are and who is going to support you politically.