It is not just racism or beauty standard although those are some factors. Anime borrows a lot from manga and traditionaly drawn manga is very time consuming to make and draw darker tones. Indeed they invented screen tones as a shortcut because fuck doing all that repetitive work manualy that probably wouldn't even look "good".

In general texturing in black and white is realy tough.

I should also note that colored manga is also quite rare specialy before the digital age. And even digital isn't a complete standard yet many artists still use traditional pen+paper method.