I think this manga is so popular because it's not just about the action, chapters like that make us closer with characters living in the world, we get to know them as people and not just some nameless background character
i think that was his intention at first, but looking at how popular the anime adaptation has gotten (which has a much less serious vibe), he probably does this to entertain the majority and give him some time for the real storyline.
I hope he doesn't just go the hxh or bleach route where theres more filler than main story though.. I really enjoy the worldbuilding and I feel like there's basically unparalleled potential with the world, at least when comparing to new-gen manga.
Don't know how to word it, half asleep. But do you think Endo-sensei does side stories to give himself a more breathable schedule so he won't burn out? Like this gives him more time to think or draw the main story. I was thinking about this around Martha's story. Idk, I should go to sleep.