Black and white can focus the reader's attention on the story and characters rather than being distracted by colors. It also has a long tradition in the manga industry.
Some manga are black and white because it's quicker for the artists to produce and it helps convey the mood and intensity without the distraction of colors. It's also a style that has been popular for a long time and has its own charm and fan base.
One reason could be that it's a cost-effective way to produce manga. Using just black and white simplifies the printing process and keeps production costs down.
Well, one reason could be that black and white manga has a long tradition and artists have mastered the techniques to convey emotions and details effectively without color. Also, printing costs are lower for black and white editions, making them more accessible to a wider audience.