I very rarely use iPhones but when I do I have no idea how anything is supposed to work without a back button.

The problem is that the definite way to go back on the iPhone is to swipe over the screen from left to right. That gets you back to where you come from every time.

The other problem is that no application trains the user doing this with for example an animated hint.

Knowing and using that makes the back button for users without disabilities superfluous.

I guess they end up being soft buttons on the screen.

In inconsistent places. In many UIs they're on the top left. In the browser it's on the bottom left?

So weird.

You can however consistently swipe from the left side of the screen to go back. There are a couple of apps which I suspect were not written by iOS users where this functionality is broken (such as Valve’s Steam iOS app), but those are far in the minority.

It isn't necessarily consistent.

I used my coworker's iPhone yesterday, opening a link from a text message, and couldn't figure out how to go back to the message. Swiping in from the left side went back... within the browser, which had no back history. I had to go to the home screen and open text messages again.

On Android, you just hit the back button and it goes back to the previous app in the stack if you launched one app from another.

It’s consistently going back in the context of the app you’re in.

If you want to go back to the previous app you can swipe from the left on the home indicator, or on older iPhones swipe from the left with force.

It is consistent but it may not be obviously consistent so I agree there is room for improvement there. The upper left back buttons are always to go to a different "screen" or function. The bottom back buttons are to navigate pages. The confusion with the browser comes simply from the fact that people mix a screen with a page because websites all look different. You're not going to a different screen within the app but you might assume so because you're going back to a different website.

That's something I loved about Windows Phone, UI was very consistent.

Yep! That’s definitely true.

They have the "Esc" key.

That generally means cancel, not back.

Indeed, but since opening dialog boxes was just about the only kind of navigation in apps back then, Esc effectively worked as a back button.