Yeah, booting from USB is something you see a lot in the data security and/or privacy-oriented circles. Because many USB boot drives are designed to be volatile, meaning nothing about the OS is actually stored on the drive. So you can nuke the whole OS just by unplugging the drive.

Basically every (smart) drug dealer who orders their supplies on Tor uses a USB drive OS, so if the cops ever bust down their door they can just yank the USB and destroy all evidence of their online orders.

But it can also be useful for test-driving a particular repo. If you ever manage to fuck things up royally, you’re just one reboot away from a fresh start.