They are in Eevee and most realtime engines because both Eevee and “most realtime engines” are Ray Tracer and Rasterizer hybrids. Cycles is a pure path tracer. Changing it into a rasterizer hybrid just for the purpose of fake rasterized volumetrics would require fundamental change to the renderer architecture which would come with a lot of drawbacks.
Second of all, you are citing literally 10 years old article. As in if a kid was born when this article was published, the kind would turn 10 a few days ago. That’s such a long time to change direction and goals, that significant portion of that article is probably not valid. Cycles is currently on it’s way to become much more than just “small studio” production render engine.
It could already be used on some of the tripe A production workloads, and it has only a few components missing to be used on almost all of them (volumetrics motion blur, proper shadow catcher…)
I do get the appeal of rasterized volumetrics. They just render so fast compared to ray traced ones. But it just makes more sense to render them in the hybrid renderers than trying to turn Cycles into one at this point.