Does a book "have to be" diverse/culture-sensitive?
I'm not someone who says a book "has to be" anything. I've experienced this throughout my life ("you have to write in Filipino", "you have to write about the poor", "you have to write what's popular"). There's nothing wrong with what they want. I don't know how it affects you, but that to me is just a formula for NOT FINISHING ANYTHING.
That said, you may have noticed that my books have a LOT of Filipinos in them. I've taken the time (in recent books) to point out when someone isn't Filipino, or is Filipino and something else, just to illustrate that yes even in Manila there's a variety of cultures one might encounter professionally, socially, etc. I've also learned that some readers will see this as too much culture, or not enough.
What do you mean, not enough culture?
Because ebook buying hasn't taken off that much yet in the Philippines, it means most of my ebook sales come from OUTSIDE of the Philippines. And because I'm up front in my author bio and book descriptions that these stories are set in the Philippines, it's reasonable to expect that I get readers trying my books because they want to learn more about my country. But then they get a story about a young woman falling in love and finding a job in the city, and maybe it's not the kind of "culture" they were expecting to see. Stories are affected by their setting, and certain cultural quirks will influence that. How much though?
I try to have my covers designed and my book descriptions written so that they don't advertise an exaggerated "cultural experience" if there isn't any, but readers will have their thoughts and ideas about a topic, and they will decide (with or without my help) whether my book meets those expectations or falls short. There's a reason though that my books are still categorized in CONTEMPORARY ROMANCE, and not, say, SOCIAL SCIENCES.
That said, I find it fascinating that other authors feel some pressure to remove traces of "culture" and others aren't "cultural" enough.