Real World Usage of Key Value coding

Hi,
This chapter is a good introduction to the key value coding but i am struggling a bit to grasp the idea from the real world use case perspective as to why/when KV should be used when the properties can be used as efficiently instead
The line in the books says :

"If key-value coding was not astonishingly useful, no one would tolerate it.”

Thoughts?

Good place to start learning: