#1 Why he should - Name recognition
RKO. Those three letters are the three most destructive letters in all of sports entertainment. They are instantly recognizable. If my initials were as cool as RKO, I'd be sure to use them as much as I could.
Lots of people know Randy Orton. Even casual fans or fans from an older generation know him. They'd probably say "he's the guy from those videos where people fall and he's edited in." Outta Nowhere was a very popular meme back in the day.
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Basically what I'm trying to say is that people recognize Orton. This is going to be very important because SmackDown is moving to Fox in a couple of months. If people are surfing through channels and they happen to see Orton, they'd probably think "hey that's Randy Orton! Is he the champion? I think so because the announcer called him the WWE Champion, plus he's got that really big belt."
Kofi Kingston, through no fault of his own, mind you, is not as well-known as Orton. People who don't watch at all probably wouldn't even notice, and lapsed fans would probably say "isn't this the guy who never wins the Royal Rumble? Isn't this the guy who is always somehow United States Champion and fighting Dolph Ziggler?"
If Orton wins at Clash of Champions, he gets to be the easily-recognizable face of SmackDown Live.