Not particularly a fan of custom fonts, but fonts are not one size fits all. Apple or Microsoft default fonts are designed for the general use case, and other fonts might be more suited in a different context. Whether that's worth the cost, that's a different question.
come on. i am not expecting to visit an art gallery when i browse the current website or your local news portal or a blog or youtube. do you really think each and every website "needs" to individually tailor fonts to their "exact millimeter position" or otherwise the result will be utter garbage?
>and other fonts might be more suited in a different context
that is why "general use case" is my point. can you point me a specific example of where my current default "noto sans 10 pt" in kde neon is NOT suited for a specific use case? i want to see that unless i use a developer decided font, i would be totally off base, i would miss the plot, i would read garbage, etc etc.