Because it breaks immersion when I see it, and I'm pretty worn over the trope of "saving fellow countrymen" as special and unique, above and beyond the laws and norms of the culture they're integrating to. I read Korean, Japanese, Western European, Chinese, French, Thai, etc. fiction. And trends emerge.
The strict in-group/out-group (you can literally draw circles and identify characters) highlights this. Take for example the bandits she literally trampled and gored to death with spiked stegosaurus -- a reverse Iron Maiden. Now look at how she treated "a fellow player".
- Are the "fellow player's" crimes any less horrific than the "standard bandit"?
- Does the Japanese legal concept of "under-14 juveniles being unaccountable for crimes" apply in an Isekai world legal system?
- Why is the author going to such lengths to show how "the world is real, these are her struggles integrating and accepting it"... yet immediately backtracks as soon as a "fellow Japanese" is introduced?