When you're extremely bored and decide to type all letters and numbers backwards to bother your friend.
John: "9876543210zyxwvutsrqponmlkjihgfedcba"
Bob: "Why did you text me that"
John: "idk bored"
Bob: "Bro I literally just told you that my dad just died"
When one individual is bored at an extraordinary level, thus typing in the characters going from right to left across their keypad and moving down a row when necessary. Only typed when one has reached the pinnacle of boredom, levels of boredom so unimaginable that they must come up with a new un-creative thing to type into search engines in order to retain the sanity their sanity. Please, go touch grass.