That's a blanket statement and like all blanket statements, is wrong (and yes, I understand the contradiction and irony of that statement).
It is not true that "all" CPUs, SSDs and graphics cards run "hot" on stock systems (whatever "stock system" is supposed to mean). In fact, in a properly configured and maintained case, with components running at the manufacturer's default settings, and the computer operating in a "comfortable" (e.g. "normal" - for humans - room temperature) environment, it is safe to say "all" CPUs, SSDs and graphics cards (that are NOT faulty) do NOT run "hot".
Might they on "
some" poorly designed systems? Yes.
Might they on "
some" systems where
the user dinks with the clocks and voltages when they don't know what they are doing? Yes.
Might they on "
some" systems operating in ambient environments
inadequately controlled by the user? Yes.
Might they on "
some" systems where
the user fails to do regular preventive maintenance (like cleaning filters and the interior of heat-trapping dust)? Yes.
When there is a high enough demand for such products to make designing, manufacturing, and distributing them for sale becomes economically feasible (read: profitable) - which most likely will never be.
Why?
Because...
Among many other reasons.
Don't forget, even if you build an immersed system in a 100 gallon fish tank, if the ambient (room) temperature gets too high, eventually the coolant liquid will get to hot to adequately cool the heat sensitive components (without some sort of expensive - to buy/build and operate - refrigeration system). And then the problem will be compounded by the fact that same coolant will take nearly forever to cool back down to safe levels - instead of nearly instantly (relatively speaking) with today's conventional cooling solutions.
Bottom line - been there, done that, not worth it... ...well, not me personally but others have and I try to learn from the mistakes of others. So I have no interest or intention of re-inventing the wheel, or the Edsel, or a better
cigarette pack holder. And I doubt any commercial builder does either.