It's just another Tuesday on your way to work and you stopped by your favorite busy coffee shop to get your caffeine fix. You set your tablet down to add the cream and, when you turn back, your laptop is gone. It's nowhere is sight, nor is the thief who stole it.
If you have a password on your laptop, it will slow the thief down; but what it doesn't stop is someone removing the hard drive and connecting it to another computer to get access to all your files, passwords, and email - that's not hard to do.
How do you protect your files? Encrypt them! With the drive encrypted, a thief can't just pull it out, hook it up and suddenly have access to all your files. This is ESPECIALLY important if you hold or have access to medical records, credit card information, or other sensitive data on your devices.