Ident' Numbers on Wings?

Simple question, but why do some aircraft (mostly outside of North America) have their tail numbers on the top of their wings?

Does this really help with aircraft identification? The only time I could think you would be above the aircraft would be in the tower, but even then, I feel like you wouldn’t have the right perspective to read the number.

Heres what I mean on the new A380



From the ATC point of view.

When the plane is under the tower, this position is undoubtedly the most clear 。

From the passenger’s point of view,

This is definitely a good place to take a picture, so you can clearly record which plane you are on, like this.

The logo and the number are very good.