[ageitgey]

If a company over-hired in non-core areas during the last two years because valuations were high, they might want to shed non-core workers that they feel that they don't really "need". But they definitely don't want to lose the best people working on the core business.

The people who take voluntary leave are often the most able to quickly find a new job (i.e. the best people). So it is not in their best interest to incentivize that.