This comment is also very misleading, as some of the best looking ttrpg's were made in the 90's, many of which only had black & white art. Artists like Tim Bradstreet, RK Post, Clint Langley, and thousands of manga artists like Katsuya Terada would strongly disagree with you.
Black and white art has higher impact and greater detail than most color counterparts, and leaves no place to hide your mistakes. Some of the greatest (IMO) art in the world is black and white line art, just look at this example from the artist Katsuya Terada: