Because there is no need. It just the usual trend/hype.
* Manjaro is Arch.
* Cachy is a patched Arch (exactly what Arch avoids, heavy patching).
* SteamOS is Arch.
* Arch is Arch.
It's about sane default packages and installers and desktop experience, as well as onboarding.
It doesn't take a lot of work to get any distro to become a good gaming machine, but it does take some work to make it a seamless turnkey gaming machine for the masses.
Of course there is a need - if you get a brand new PC don't you want it to perform as it should? Or do you want to wait another 2 years for that to happen?
Also very few people want to tinker with every single little thing, they want a nice stable base that does what you expect and build upon it - that's why most people were fine with previous versions of windows. So if cachy fixes 95% of the issues for you, why not go for it? Saving time and headache is a reasonable thing for a focused distro.
> Any useful and stable patch will be merged by upstream. That is why using CachyOS or ClearLinux isn’t beneficial in long term.
Seems like you're blinded by your own context, if CachyOS for example see patches, integrate them earlier than upstream, and let user use them today rather than "long term", how is that not useful or beneficial to the users who want/needs that?
Besides, testing patches this way sounds like it'll have wider impact in the community than just the distro that integrated the patch, as it'll have a way wider testing userbase then. Isn't that also good long term?