How come when you set up an iPhone, the home screen apps are in different positions for different phones?

Like, on one iPhone 6, at first, the message app is in the top-left corner, and the mail is at the bottom, and on another iphone 6, they switch spaces?

The home lets you customize which icons appear on the home screen, and the positions of the icons. Apple defaults are the same for any given release, but the USERS have individual preferences.