Engadget
External drives can still be working, even when it looks like they're idle.
You might have done this for years without any serious repercussions, leading you to assume that properly ejecting external drives is just old computer advice that stuck around past when it was relevant.
Even after the file transfer bar completes, your computer doesn't always end its business with your external drive. Beneath the surface, your operating system might still be handling tasks like writing cached data from memory and sorting out file directories. Taking a few seconds to eject an external drive tells your computer to wrap up whatever process is going on before you unplug it.
Many times, nothing happens when you unplug a drive without ejecting, but the action always carries some risk. The negative results of not properly ejecting an external drive are the same across Windows, Mac and Linux. If a transfer was ongoing, either in the foreground or background, pulling the drive will leave the process incomplete and files potentially corrupted.
What's worse, file corruption can be silent, so you might delete the original file thinking it was copied, only to later find the version on your expensive flash drive is corrupted.
A file system is your drive's record of what is where and what is what. The "Disk Not Ejected Properly" on Mac isn't a sign of data loss; it's a warning.
In cases, neglecting to eject your external drive can lead to partition table damage.
How safe it is to suddenly eject external drives depends on your operating system.