The proof is in the pudding:

> PikaOS Linux is a Linux distribution based on Debian's cutting-edge "Unstable" branch [...] [1]

Trademark and reach.

Gaming distributions don't run a stable version of Linux distributions. They're always a spin-off from one of the popular Linux distributions (rebasing every once in a while), with additional changes tailored towards gaming.

Now, you cannot just say I call my distribution Debian GNU/Linux Gaming Edition. If you would, you'd need to work under the umbrella of Debian. With a different name, you differentiate from Debian, while you can keep the advantages of their framework (hello Ubuntu).

[1] https://distrowatch.com/pikaos