End-of-life software turns patching into replacement

Once a product is unsupported, patching is no longer available as an answer, and the problem becomes a project.

That is why it slips. Applying an update is an afternoon; replacing a system is a budget, a migration and a conversation with whoever depends on it. The exposure accumulates during the years it takes to schedule that conversation, which is why end-of-life dates need planning for well before they arrive.