I've seen this tired argument so many times, and the most curious thing is that it never comes from people who receive their degrees in linguistics and spend years living in the countries whose languages they study, having plenty of firsthand contact with their cultures. Really makes you think what happens there that makes them drop this notion for good, huh? Why is it that they go out of their way to ensure that everything is properly translated and even—gasp!—localized?
The answer is entirely straightforward: actual translators want readers to experience dialogues and other text in the story like characters themselves do. For a Japanese person reading a Japanese manga, these would just be perfectly normal family interactions. So for an English language native reading an English translation of a manga, they should also sound like perfectly normal family interactions—not an unsolicited social studies presentation. By fully comprehending the writer's intent and matching the characters' speech tone, vocabulary, and flow to their nearest analogs in the target language, and hence conveying the entire experience as closely as feasible, you show respect to the author, their culture, their language, and most importantly the readers. You've taken effort to understand the intricacies and commonalities of both cultures and connected the dots such that the transition is seamless. That's also how you can tell a good translation from a bad one even if you don't know the source language: a good translation always aims to sound natural in the target language and uses a wide arsenal of tools to that end; a bad translation goes for canned phrasing, bare-bones punctuation, and so on at every opportunity—just like here. In a sense, it's not that different from good writing vs. bad writing, and it's a grave sin to make good writing appear worse than it is because of translator's ineptitude.
Words are just tools to convey intent. This simple concept is the cornerstone of translation as a discipline, and it takes enormous amounts of skill and experience to master. And the journey there starts with relinquishing the idea that any specific words in the original script are sacred and should be preserved over the intent behind them. By picking and choosing which words to leave untranslated for such shallow reasons and translating everything else with all the grace, attention, and fluency of a diazepam addict operating a stapler, you engage in a stuffy weeb circle-jerk between people who don't really care to study languages or cultures but sure like to pretend that they do. It's not a good place; respect doesn't live there.
