[iOS 9] It is now easier to distinguish between uppercase and lowercase letters during full keyboard input.

As the title suggests, updating to iOS 9 has made it easier to distinguish between uppercase and lowercase letters during full keyboard input, which is a nice feature.

Previously, tapping the shift key changed the color of the shift key, and the engravings on the alphabet keys remained in uppercase.
So I used the color of the shift key to distinguish between uppercase and lowercase letters.
Previously, it was often confusing whether the shift key was pressed or not.

However, in iOS 9...

The engravings on the alphabet keys are also different for uppercase and lowercase letters, greatly improving visibility.

While I'm happy about this improved functionality, I wonder why it wasn't done before?

Addendum (2015/09/24)
You can also hide the lowercase keys like in iOS 8 and earlier.

[Related]: iOS 9 released, enhanced search function, iPad function expansion, new memo design, etc.