Fillers in ABS are not terribly common in the plastics industry. While it is possible that there are more, typically ABS is only filled/reinforced (note that these two are not the same thing) with glass "bead", glass fiber, or wollastonite silicate (according to my reference book). All three applications are a reinforcement, with fillers such as wood or cellulose rarely occurring in my experience.

Carbon reinforcement is certainly possible, and in fact you can buy carbon reinforced abs here:
https://www.3dxtech.com/carbonx-carb...ting-filament/

And likely other companies make some as well.

There are some chemical concerns with coupling the material to the reinforcement or filler, however the primary reason is most likely as CA stated - ABS is simply not a very consumer friendly filament and is far less popular. There just isn't the demand for it like there is in the molding industry, where we absolutely love working with it.

Metals are simply cosmetic in nature for most applications and again in 3D printing is by virtue of low demand. In molding, if we need a metallic sheen on an ABS part we would simply use a secondary process to plate the part. It's not very common in plastics as a filler or reinforcement either simply because of the higher weight to strength compared to fibers.

I think CA has some input on plating?