I think Chinese people do, at least that was my experience of peers at university (in the UK) - many would wonder around either holding phone perpendicular to face, or with an earphone wire microphone strapped around their mouth having essentially asynchronous telephone conversations. Best of both, in a way?

Maybe it's also about language - easier to speak Mandarin than type or draw it on a touchscreen? I don't know.

they are just lazy or too old, actually typing simplified Chinese it's faster than English, amount of characters you have to type/swipe to deliver same content it's much lower than with latin languages due to length of words and primitive grammar (even more primitive than English and that's already something compared to European languages with tons of grammatical cases and forms for each word and multiple plurals and genders, heck Chinese doesn't even have singular, if they would switch to pinyin they could conquer the world)

Maybe the feature doesn’t get much use because it’s shit in iMessage? Also sound quality is horrible compared to WhatsApp. In my case: I dictate up to 10 seconds. I use voice messages for everything longer.