They do hire, actually. Security companies are smart, but there are smarter hackers as well. That's why cryptocurrency ownership is an individual responsibility. Just think of you owning a huge stash of gold coins: you buy a vault for security, and may hire a personnel to guard your property, but if you are still irresponsible as an owner - like announcing to the world you have a vault full of gold coins in your house, then smart thieves will make plans on how to rob you.