Running a Live Linux CD or USB is a convenient way to perform a number of tasks when an installed OS is not necessary.
Do you think an operating system should always be installed on the hard disk of a computer?
It was true for me up until a certain point. Things changed when Knoppix Live CD was released by Klaus Knopper in 2000.
Knoppix was a pioneer in Live CD for Linux, and it still remains one of the most respectable Linux distributions. Of course, Knoppix is not alone. There are many more Linux distributions available on the market now that can run in Live mode.