Why is there very little ABS composite filaments?

[curious aardvark]

abs is a lot harder to print with than pla. It also expands more when heated and shrinks more when cooled.

So any mix of abs and a non-plastic material is just not going to perform as well as the same non-plastic material mixed with pla, which is a lot more thermically stable.

You can get abs mixed with carbon of various 'flavours'.
But that's pretty much it.

Also the specialist blended filaments are expensive, so the manufacturers want it to be printable on as many machines as possible. And abs is just not worth using on an unenclosed printer with an unheated print volume.

Also a lot of manufacturers are now producing printers without heated beds - a massive mistake in my opinion - so and fancy abs blends just wouldn't work at all.
Abs prints are often treated with acetone for one reason or another, again this could react with any inclusions.

There are probably other reasons as well.