This feature was removed in M13. It made its glorious debut in M12 and then it was retired along with several other innovative features over the years that make it in only to be removed.
I actually would love to see the surprise onside kick return as part of a new feature - auto kick. Similar to auto-passing, I think this would be a great tool for us "sim" style players and could alleviate a big gripe of mine with online head to head games within CCM. That gripe would be the horrible timing of the lag, which seems to bite me in the backside over and over again in the kicking/punting game.
Think of it from a multi-player online CCM view. As it is right now, nearly everyone looks for the cheapest kicker with high KPW, as kicking is too easy, my lag issues not withstanding. If you had auto-kick as a feature (on/of league setting) then you may force people to spend more on special teams and actually have people looking at the kick accuracy ratings for the first time since, well did it ever matter in Madden ever?