Monochromatic art is attractive to many people on its own. I do a lot of ink-stipple projects, and a LOT of people say "you should add a splash of color!"

But those people don't have any interest in then buying that piece of art.

They just feel the need to push their own preferred aesthetic on the monochromatic piece- as if to imply the ink work is "missing" color.

It's not. The lack of color is the point.

There are people who do that style you are talking about, but if someone doesn't do it, it's an active choice. You're not recommending a novel idea. They've considered it, and rejected it already.