It’s cheaper. In Japan manga volumes are about 700 yen, which is about $5 currently. No budget for color printing there. Manga is often drawn by one person who is already massively overworked just to hit serialization deadlines, so no time (nor budget for assistants) for coloring.
If people want to learn more about all of that in a fun way, they should read the “Bakuman” manga by the authors of Death Note, the story of two mangaka and their journey to becoming authors for Jump magazine. I really enjoyed it myself.
Sometimes, the first few pages are colored but the rest are black and white. Why is that?
Some will have the first page(s) in color, or a full scene somewhere in the middle. It’s to get or keep your attention, and show off the artist’s ability with color added, while still staying cheap to print for the rest of the manga. Best of both worlds kinda.
Reduces the printing cost I imagine.
I think comic books as well as comic strips in newspapers used to do the same thing. Old printing press technology had you do a separate pass through a machine for each color layer so the more colors the more time and money.
