There are actually some true Black on Black Tartans.

For just one example Marton Mills produces the Ben Dubh, Black Isle, and Black Shadow Tartans. These three are available in 13oz Wool.

These are true Black on Black Tartans. You cannot see the Tartan Pattern until you turn the fabric or it moves in the light.

There are basically two ways to produce a Black on Black Tartan Pattern in fabric.
One is the twist the yarns of the Weft in one direction and twist the yarns of the Warp in the opposite direction.
The other is to weave with the Warp true Black and the weft with a very dark Gray. Then after the fabric is woven re-dye the fabric all Black.

I have tried to get some photos of some of the Kilts we have made from the Ben Dubh Tartan but without movement they don't allow you to see the Tartan Pattern.

They are also a pain to pleat up which may be the reason most less expensive makers do not use them.