That's right.

Nowadays many linux CDs/DVDs/USB sticks start by booting into a live system, and then offer you to install it.

Back in the days when Knoppix was popular, the major distros only had normal installers, so you needed a free partition for installation (or resize an existing windows partition to make room, which was very risky).

As a 9 year old in late 2000, Knoppix was my introduction to Linux. I wasn't asked to install Linux on the family computer (not that I knew how to).

I don't remember how I first heard about Linux or Knoppix but I do remember those first magical moments using it. While I've had many influences Knoppix definitely was an early influence on my tech interests because it was so easy to start.

A worthy present-day update this way of lowering the barrier of entry would be a convenient, pre-configured way of running the same persistent set of configuration state and user home from either a boot media start or within a virtualized environment. Virtual container with optional full reboot. Does something like this exist?

There is also a games version with quite a few games.