Why do iPhones have the same lock screen picture in movies?

Am I the only one who has noticed this?
Every movie I see with an iPhone, the lock screen is of the raindrops.
I don't think I have seen any different but I might just not be noticing it if there are different ones.

This might be a stupid question with an obvious answer but I honestly have no idea.
Why is this? Or why would this be?

They use a default lock screen.

They actually most of the time aren't real phones, they're just props. But that's only some of the time.