I used to use this on a CD-ROM, for SSH-ing into my personal server to check email (from work or SO's place), when I didn't have a laptop or handheld with me. USB flash drives often didn't boot by default on PC hardware, but CD-ROMs did.

Later, I made an immutable "Swiss Army knife" USB stick distro called LilDeb, based on Debian Live. And literally carried it on a Swiss Army pocketknife on my keychain. LilDeb was implemented in two big shell scripts, which you can still see at: https://www.neilvandyke.org/lildeb/