#1 To make the show unpredictable
One of the issues that WWE is facing right now is the fact that while people are watching the show, they are not necessarily watching it live every week. You make the WWE Universe tune in live to watch the show when there's an element of uncertainty running through it.
One may argue that the product is a lot more predictable than it used to be back in the Attitude Era, during the time of The Rock and Stone Cold Steve Austin.
It's a different era and a different audience, but the one thing that's for certain is that WWE still needs viewership to be healthy to keep all the network executives happy.
While this may not be the same level of 'surprising' as Kurt Angle coming in with a milk truck, it is still a genuine surprise for this era. Ricochet pinning McIntyre is a genuine surprise for sure.