Because those are the parts of the world where Apple makes most of its sales. Oh wait, no, outside of NA, EU, and Japan, their marketshare is now minuscule compared to Android.
But wait, there's a new "cheap" iPhone that's targeted at those other markets, right? Oh nevermind, that one doesn't have a fingerprint sensor.
... you realize there are large parts of the US itself where gloves aren't a thing during winter time, right? Shit, I grew up above the 49th parallel and didn't wear gloves regularly throughout the year.
But wait, there's a new "cheap" iPhone that's targeted at those other markets, right? Oh nevermind, that one doesn't have a fingerprint sensor.