In Linux operating systems, drives remain unmounted until you open/mount them. As a result, any file residing in an unmounted drive cannot be accessed, like say, from your Firefox history or when you open a saved document from somewhere.
My intuition tells me that there must be some benefit of this feature. What is it?
Linux systems can be configured to have everything mounted by default. However, they are not usually set up to do so, for safety and security reasons.
Plus the fact that only root is generally permitted by default to mount devices and file-systems on such systems, also for safety and security measures.
Safety and security can refer to viruses, hackers, malware, fraud, phishing, spam identity theft, etc.