Miyazaki has used the art of animation to study the major problem of adult life

I'm going to guess that for an English speaking market, there is a certain expectation for Miyazaki movies that has to do with whimsicality, children and some sort of anthropomorphized animal. and so that's the title format that they believe will sell better.

Americans in particular are likely to be put off by something that sounds like it's questioning their life decisions.

Titles are very frequently changed, this is because titles are supposed to sound catchy and what sounds catchy in one language often does not in another. Spirited Away in Japanese was also literally more so “Sen and Tihiro's mysterious disappearance. The Vanishing*'s original Dutch title was “trail-less” literally, which sounds good in Dutch, but very poor in English though I suppose “without a trail” would work.

Not the grandparent poster, but... I don't have any linguistic insight (there were some, with the sister posts about "How do you live" sounding condescending in English?), but a practical one.

I just saw the film last Sunday. The title "How do you live" has hardly any strong connection to the contents of the film. The film doesn't pose that question to the audience. The film doesn't much seem to explore the theme. (A little? Maybe, but not to the extent one would expect from the title.) The titular book by Yoshino Genzaburo (whose plot has no overt resemblance to the movie's plot) appears on the screen briefly, and one could guess that it'll prove a "Chekhov's gun" kind of an item, but this trope is entirely averted.

I think that it is only through a "meta" lense that sees the film as an autobiographical work, with a Miyazaki self-insert as two different characters (Mahito and the great uncle), that the title starts to make sense. It is Miyazaki's attempt to _answer_ the question – in the scope and perspective of his own life and work.

I doubt that this perspective would be readily available for an American viewer. They are unlikely to know the book and they are unlikely to be aware what kind of a person Miyazaki is, what is his connection to Ghibli, his movies and to his son Goro, something a Japanese viewer is much more likely to be aware through various interviews, documentaries and news coverage. Miyazaki has called this movie his "testament" to his grandson, and this certainly makes you consider these things.

If anything, the title "How do you live" would be misleading and disappointing to an American viewer. It makes the film sound more philosophical than what they are going to walk away with.